There are something like 21 different characters you can control, each with different stats in the areas of health, jumping ability, speed, weight (how much they float in the air), weapon type, and strength.   At the beginning there's a pretty steady flow of new characters introduced, but the last couple of stages offer few surprises.  There are two exceptions, though; the laser guy can only be found in one area in the last level of the game, and there's also a super secret character you can only get if you managed to collect three keys by the end.

The bad news: each character has a total of one (!) attack.  This might have been acceptable in '91, but it's hard not to think about what it could have been if Avenging Spirit took more of a b'mup approach to the gameplay.  Offering totally different movesets along with the changes in attributes could have pushed this game over the edge in terms of sheer greatness, but as it is each character feels way too limited.

Yeah, this is just an action platform game, but that doesn't mean they couldn't have given us more to work with.  I mean, say you bought a porno that touts on the cover that it has 21 different girls, but then you watch it and see that none of them ever move out of missionary.  Lame. 

Like a bad porno, Avenging Spirit has no money shot.  What you do in the first level is exactly the same thing you'll be doing the whole way through, except of course a few boss fights.  It's kind of odd that there's such extreme variety when it comes to playable characters, but zero variety in level and game design.
Well, I shouldn't say zero per say - there is this one level where it's less of a "point A to point B" affair and more of a "search through all the rooms and backtrack until you find the right way" kind of deal.  That doesn't exactly work in the game's favor though; it's more annoying than anything else and really doesn't add the kind of variety I was looking for.

If it's sounding like everything in Avenging Spirit is relying on the character swapping gimmick in order to be fun, that's because...well, it is.  Take away the different characters, and you're left with a decidedly sub-par game.  While it's definitely an idea that I would love to see taken to the next level, maybe in a b'mup or something, the idea isn't solid enough to completely carry a game.  Without a solid base built around it, you're left with nothing but a gimmick. 
So, let's take a look at the game while putting the gimmick out of our minds.  First we have the levels, which are decidedly tile-based and offer little pizazz or variety; then you have the action, which is dumbed down to an extremely basic level and offers nothing in the way of variety or intensity; and finally we have the actual platforming, which is marred due to poor controls.

Those platforming controls are especially irritating in the levels that require you to jump onto the tiniest little platforms you ever did see.  Those work fine in games like Super Mario Bros. where you're given enough control to be able to manage them, but somebody really dropped the ball on the controls in Avenging Spirit.  The biggest downfall is the fact that you can't make your character simply fall downwards.  When you're in the air, you're stuck between either going left or going right at the same angle and speed.  So, for instance, if you're in the air over a platform and just want to go straight down in order to land on it, you'll have to wiggle the stick left and right to snake down onto it.  Watching someone trying to platform in Avenging Spirit is like watching Nick Nolte trying to parallel park, except you're not left with the amusing mug shots to look at afterwards. 
Unlike the gimmick in Altered Beast, however, this one actually does go a long way towards making up for the game's shortcomings.  It's great knowing that any enemy you encounter can be controlled if you want to, and you'll have a blast trying 'em all out.  It's always annoying when you see a game that tries to skate by on the heels of a single gimmick (thus me ragging on the game so much), but at the end of the day you really are looking at a fairly solid and fun game.  There are better options out there, but at least this one is something a bit different.  Like the aforementioned porno this isn't likely to hold your attention for more than half an hour tops, but at least you can walk away from this one without the filthy stench of shame getting all up in your undies.