SSJ4 Vegito as he has lightning in his hand.
SSJ4 Vegito in his legendary state.
Vegito used Super Saiyan 4 against Omega Shenron in a what if. Vegito turns Super Saiyan 4 when he gets angry and breaks the walls and buildings. Since his fusion is permanent, he can continue to fight and is stuck into that form permanently. Which mean he's so strong he could kill Omegea Shenron with trouble on his hands.