You can shoot the tentacles while they're still in the ground, that way you don't get smashed. Other than that, just shoot him until he dies. If you have the ammo and a machine gun he goes down pretty easy.

i find the easyest method is to save the ammo from the mrl you get earlyer and then shoot
him with it just as he shoves his hand in the ground and cracks begin to form. If timed
right it will stop the tentacles from attacking you and do lots of damage. then dodge him
as he jumps down and shoot him with another weapon. if you save all your mrl ammo to stop
the tenticles this battle gets pretty easy-deadbowser

I am so stuck. I don't feel like I have the right ammo with me but how do I get the ammo I
need to get these two guys?

I beat the mutant with only a handgun.

1:its impossible
2:cyber twins are ivan just shoot anti tank gun
3:let tenticles hit u and just focus on nemise's head(mutant)
4:car its impossible to kill nemsis with handgun

he is hard all you need to do is have good ammo and good wepons when tentacles appear use
the hand gun so then you dont waste good guns and ammo.i herd you can get unlimmited ammo
if you get an s in each stage evan on specials and bonesis oh and theres this big guy with
yellow gl***es hes hard but when you get the rocket luncher he gets easy to kill.renember
save ammo!!!!!!!its ver inportant look im fighting that bif new b.o.w guy and i almost
beat him by saving ammo when he mewtated i lost ammo,see save ammo.

i kill him to with a handgun