He didn't personally whack Big Paul. He stood by and watched the hit take place, but he didn't pull the trigger.

Gotti, I believe, was overheard on tape saying that the DeMeo crew killed more people before breakfast than than they, the Gotti crew, had ever killed.

Also, consider DeMeo's body count. The man was an accomplished killer and butcher. A fact that, no doubt, weighed heavily on Gotti's decision not to try and take on DeMeo himself.