Chrissy wasn't the most loyal to Tony. Many times, he doesn't listen to his boss when he told to. He was about to flip on Tony til he saw at the gas station, bum family and he didn't want to live like that. Made the movie about "Tony", always wanna leave the mafia, wanna do the Hollywood. He's complaining too much, couldn't stay off drugs. Trust me, if FBI busted him that he's on drug and He will def flip on Tony so that's why Tony had to kill him. I can understand his frustrated with Tony when Tony made some bad decisions.

Silvio is only one of the most loyal to Tony.