( Note: For this entry I'm going to use the term "encounter" to describe a fight the player must complete to proceed in the game).
Develop a Baseline: A "baseline" for this entry can be defined as the absolute maximum situation that the player can deal with using their basic skill set. There is no exact science to determining this and several factors can be used, some of which are topics mention later in this entry. For example in God Hand the player can easily fight one normal enemy at a time but throw in another enemy and the player will need to step up their game. While in God of War Kratos can usually handle anywhere from one to six normal enemies at a time.
The reason why this is important is that by developing a baseline it will allow the designer to understand the balance behind each encounter with enemies and scale them to give the player a fair challenge without overloading them. A side bonus is that as a designer you can start to see how the various groups of enemies will play out against the player. Such as can the player deal with five un armed enemies, or three sword wielding enemies or three normal enemies and two large enemies?. Now creating an exact baseline is impossible, while the designer can see a lot from looking at the mechanics involved, player skill level is still the main factor and the only way to really gauge that is to play test the hell out of your game and even that won't give you a perfect blueprint.
Another importance use of the baseline is to also determine the weakest parts of your combat system. The reason of course is to not design your encounters around these sections. Yes they will be challenging but it will be like trying to do jumping jacks with your hands handcuff. An example of this in action would be with Ninja Gaiden 2, in the first one Ryu is incredibly capable of handling enemies in close range but long range fighting was a bit troublesome. Ryu can attack enemies while zoomed in with a bow but that leaves you open to any attacks. He can also attack without zooming in but it is very hard to hit the enemies you want due to a lack of lock on and the camera.
Team Ninja was smart and kept the encounters mainly to close range with a few sections that required the bow. However with Ninja Gaiden 2 the very first level involves Ryu dealing with long range snipers while having to fight enemies close range. Then a few chapters in a boss fight were all about having to use the bow to attack him while the camera was never pointing in the right direction. Eventually this and a few other questionable decisions made me give up playing Ninja Gaiden 2.
Panic Button: The concept of a "panic button" has been in most action titles and is used as a way to get out of a sticky situation. The common themes behind a panic button in action titles is that most likely it will make the player invulnerable while it's being used and is an excellent way of dealing with a lot of enemies, in Ninja Gaiden Black Ryu had his ninja magic attacks while Dante of the Devil May Cry series has demon form.
To have or not have a panic button mechanic is up to the designer however it is important not to balance your encounters with the panic button in mind. The reason is that if you design a fight that requires the panic button and the player has already used it, they will be in a lot of trouble.
Difficulty: I've talked about the concept and usage of difficulty levels in past entries and I feel that with action titles difficulty settings can be very hard to balance. The reason goes back to player skill, for some players "normal" could be easy for them and for others it could be too hard. Tweaking stats in action games in my opinion is not the right way to go. You’re not making the encounters harder for players but instead lowering the amount of mistakes the player can make before they will lose. If an encounter is annoying on medium, then it becomes frustrating on hard.
Ninja Gaiden Black in my opinion still ranks as the best action game to use difficulty levels. On every setting, enemy stats do not change at all, the blue ninja on "easy" hits as hard as they do on "very hard". The difference is that when you are playing on "very hard" you're not going to run into the blue ninja, but his bad-ass brother the red ninja who has more tricks up his sleeve.
Because of the skill level required to play action games, the overall difficulty curve of the game should actually decrease the further the player gets, as their skill improves they should be able to handle fights easily. For example I had a friend over once who tried Ninja Gaiden Black on normal and couldn't even get past the first boss fight. When I play NGB I cannot play the game on normal anymore after playing it on very hard because I find it too boring.
Weapons: Another detail that the designer must make a decision on. Most often action titles that are more about hand to hand combat won't have additional weapons the player can use (picking up a pipe or a temporary weapon doesn't count as it isn't indefinite). In order to make a good weapon it must serve the purpose of adding utility to the player's arsenal. There should be a reason to switch from an axe to a sword for example.
God of War 3 was horrible in this regard, Kratos has four main weapons and three of them are bladed weapons attached to chains. There's no real purpose or reason to switch between them. Contrast this to Ninja Gaiden Black where each weapon has a different move set and purpose. Ryu's dragon sword is different compared to the bow staff or berserker sword and there is a tactical reason to switch between them.
The reigning king on this matter should be obvious to those who have read my past entry on the genre is Devil May Cry 3. Not only is each weapon different from an aesthetic standpoint but they also have completely different combos and attack styles. You weren't going to confuse the Beowulf gauntlets with Dante's rebellion. Throw in styles that altered things further and the ability to switch between weapons in mid attack and the attack options became astounding.
The best defense ... is still a good defense: Don't let that popular mantra fool you, defensive options are important for any action game. There must always be a way to mitigate damage because trading blow for blow in any action game will get you killed. In my opinion there are two broad categories for defense: passive and reactive.
Passive defense are mechanics that allow the player to avoid damage with very little risk, such as evasive rolls, a block and jumping out of the way. Some titles make up for allowing the player to block by having some enemies have unblock-able attacks. With these types of actions the player will either avoid the damage or get punch in the face but it still gives them a viable tactic to use.
Reactive defense are mechanics that allow the player to effectively punish the enemy for attacking them, the best example would be counterattacks. These types of mechanics have a big risk/reward factor as using them correctly not only mitigates all damage but also does a sizable amount to the enemy in question. Of course missing the chance means the player is going to get hit with the full force of the attack.
The more defensive options the player has the better in my opinion, my idea for an action game features at least 5 different ways of defending from attacks. The reason that you want a lot of them in my opinion is that it will allow you to up the ante when designing encounters. Let's say you have a "professional boxer" type enemy whose punches are so strong that he will break through your standard block every time. This will require the player to switch to another option to deal with those types of enemies.
One detail to avoid is only having one main form of defense, because if you design enemies or encounters to nullify that ability then you are basically screwing the player. In Bayonetta, the player has access to one defense option for the majority of the game and that is evading. To offset this, the designers reward players who have good timing with witch time, allowing the player to slow down time after dodging right before an attack connects. However later on in the game the player will encounter enemies who will not trigger witch time when you dodge their attacks and some sections that nullify it.
The big problem is that when you take away this feature Bayonetta's combat system falls apart in my opinion. Her attacks rarely stagger enemies meaning that you rely on witch time to get in and attack them. Without it the game becomes frustrating to play. To be fair the game does allow you to buy an item that allows counterattacks but with a huge price tag means that most players will not be able to buy it until much later in the game.
Upgrades: Along with difficulty levels I'm not a fan of a lot of upgrades in action titles. The reason goes back to the difficulty curve that should be in action titles. The player should be improving their skills at the game to make the game easier, not purchase uber upgrades to trivialize the action. Another effect of this is moving important mechanics to the upgrade system to be used as a reward. This is a bad design decision in my opinion, you should not "reward" the player with vital mechanics that could have been used in the first place.
I hated God of War 2 for this issue, starting out Kratos lacks the ability to counterattack enemies and have to play through a good portion of the game before getting the upgrade. Ironically fighting a boss which the ability to counterattack would have made things a lot easier.
The best use of upgrades is to supplement the player's skill and reward them with more options to use in a fight. In Devil May Cry 3 and Ninja Gaiden Black, both games feature weapon upgrades but besides an increase in attack damage they mainly add new combos for the weapon. What this meant is that getting these upgrades isn't going to make me a better player, but will give me more options to use in combat and work well with my existing skills. The key is at the start to give the player enough tools to survive and reward them with more options to add to their strategy,
Health: I haven't seen too many discussions about the health system in action titles, most likely as the same model of having to find health items have been used since its inception. I feel however that there should be a change in this regard, recently Ninja Gaiden 2 tested the waters by having a portion of Ryu's health regenerate after combat. In my opinion I'm in favor of a full regenerating health system after combat. The reason is that the designer will no longer have to worry about health placement or if a player will have enough health for the next encounter.
By removing that constraint the designer can start developing off the wall encounters and truly test the player's skill. The problem with the current system in my opinion is that it becomes an "elephant in the room" in the sense that the rest of the systems and design have to be built around it. For example if a game requires the player to fight through twenty encounters in a row before getting a health item and the player doesn't have enough health to finish #20 then they are screwed. This mechanic to me feels like a left over from the old days as an arbitrary decision to make the game harder when it doesn't need to be.
In my mind the three best action titles so far would still be Ninja Gaiden Black, Devil May Cry 3, and God Hand in that order. Having played almost every major action title this year (still waiting on Dante's Inferno to go down a bit further), I've yet to see one that could knock one of my top three off its pedestal. You should not need to dumb down your action game but give the player the right tools required to step up.