Here's some tips for the game:
A.T.P. engineers :The first A.T.P. engineers appear in stage 1-E [Recon hut].It's recommended to play as Sanford on these levels cause his hook always comes back after throwing.If you throw a weapon it ignores TAC-BARs.
A.T.P. soldats:the same tips like with A.T.P engineers but they can do flipping dodge.If you drain an A.T.P. soldat's TAC-bar and he dodges shoot him imediatly after he lands.
G03LMs and G03LM mk2s : If your melee weapon isn't very powerful try to knock down theyr helmets unarmed because you can't dodge when armed with melee weapon.G03LMs will always ignore your TAC-bar and knock you down when punching or using weapon at close range.Their attacks are unblockable.
Special attack : if you come very close to the enemy that performs it you won't be hit.Always try to dodge because you can block it only when playing Hank or Dr. Christoff (Dr. Christoff can block special attacks and deflect bullets only in stage1.5 E Vaults )
Phobos : he's big and highly skilled.He can take high amounts of damage but always will dodge or block (bullets can be deflected but nexus bolts and slam attacks can't be blocked).Only fight other enemies like zombies,riot guards etc. and wait until he runs out of ammo so when he uses his sword try to hit him many times with magic/come close to him to make him use his sword and hit him with nexus bolt and repeat that until he's dead.
Sleepwalker patients:They can be revived 3 times but after the 3rd death will explode(if not decapitated or killed by a zombie or abomination).The explosions will injure anything including other opponenets so you can use them as timebombs.They cannot be zombified.Sleepwalker experiments are about G03LM sized versions and will never explode.
Riot guards: The same tips like with A.T.P. soldats.If a riot guard is grabbed by a zombie hit him with a nexus bolt before he's zombified.
If there's many kinds of enemies in one room leave them fight each other (but if zombies are fighting agents first kill the agents).Zombies will fight even abominations.Abominations : After reduced to half health they will free their arms . During their first stage they can drop-kick their foes (like on the left picture) knocking them down.In their second stage they can only grab their enemies without disarming them so it's easier to finish them with melee weapons (blunt weapons are more effective on them).They can't be zombified.
Zombies: If a zombie(or an abomination) tries to grab you and you block there's a chance that it won't succeed.They can kill even sleepwalker patients and abominations with one bite.If somebody's head is bitten off by a zombie he won't turn into one.If you're playing zombie arena mode don't use the m203 grenade launcher because it will only knock them down without doing serious damage but it has small capacity.