From what I recall you saying, Bill is more neutral and Antoine is more evil. Bill would probably have the people lending what help they could or offer distractions against Antoine. Though Antoine has teeth, Bill could try and rush him and gore Antoine with his horns.
Or maybe Bill just helps Antoine get off sexually and Antoine calls it a day and stops rampaging.

Yes, you are right, Bill and Antoine are both tough guys to be defeated.

All the blood on their enormous bodies are all from little human they have crushed during the fight, intended or not. After all, Bill is also a behemoth around 20 KMs, you can't say his feet won't crush building and human even he is neutral . The physics rules could not make exceptions.

Physically, Bill could help Antoine to get off some need, but it would aroused Bill too, it's hard to say which way will cost less human lifes.

But anyway, cost only several city blocks to save the hold city, human is still the biggest winner here anyway.