I  feel like nobody realises or talks about this part of the story revealed in Trevor's conversation with wade after he kills Floyd and Debra in the mission Hang Ten.

 It was revealed to us that Wade met Trevor as a drug dealer who then went on to kill Wade's friends that he came with to a gathering. He then lies to Wade and convinces him that his friends abandoned him to take him under his wing. 

So essentially Trevor meets a mentally disabled customer , murders his friends , manipulates him into thinking they abandoned him , convinces Wade to stay with him and then beats and abuses him as he forces him to be his slave. 

On top of that he then goes on to force his honest by the rules cousin (Floyd) to help him run a robbery from his girlfriend's (Debra) condo. And then later kills Floyd and Debra. Although they did  threaten Trevor first he was a guy that had just kicked open their door so they had every right to tell him to leave with force. 

He was then cruel enough to tell wade exactly what he did to him to his face knowing he was too dumb to realise just so he could further manipulate him into thinking Trevor was some kind of trustworthy protector.   
  
I know he eats people and does other various psychotic stuff but this was extremely dark even for Trevor. In fact it's probably the darkest thing in the game and had a high emotional impact on me and is the sickest thing in GTA V. This probably cements Trevor as the most evil GTA protagonist for me. 

And i know Micheal tried to get his own best friend killed to save himself like a serpent but Trevor is a much bigger threat to society and deserved to get taken out more. 

What Trevor did to wade was the worst thing he's ever done and makes option A highly justifiable