#1: BRANDON WHITTAKER:
He is serprisingly "easy" as long as 당신 have really good food, like wine, and streak.
Have the 칼, 나이프 gloves and when he jumps out of the stall, attack away.
Or, even 더 많이 easy. Get a sniper and a pistol, stand near the entrance, wait till he leaps out of the stall, and than have him chase 당신 out of the bathroom, he can only go so far, so wait till he jumps at you, dodge it, and shoot at him when he's running back to the bathroom.
And than just finish him off with the pistol when 당신 run out of sniper bullets (if done properly, 당신 won't lose any health)..
#2: SEYMOUR REDDING:
Get the drill/spear, thing, and stab the shit out of him, don't bother healing, just do that afterwards..
#3: SGT. DWILIGHT BOYKIN:
It says your NOT suppose to use guns.
But ironally, two snipers is the easiest way to kill him (though not EASY easy)..
Get the 칼, 나이프 gloves, kick jump him, attack him when he'as down, than dodge as he's getting up, wait till he's done the spin thing he dose, and if your fast enough 당신 can jump kick him when's dizzy (repeat this pattern).
But this isn't always as easy as if sounds, so have lots of health..
Probably the easiest way, is to get the MG gun, and shoot the shit out of him..