OMG Forget the bosses in the main story line has anyone tried to defeat these two Yiazmat or Omega Mark XII?

Yiazmat is the worst one with 50,112,254 HP it is the biggest pain in the butt ever! Next to that it would have to be Omega Mark XII with 10,370,699 HP.

Right when I get down to almost killing them they kill me.!.!