A bit off topic here, but having Carlo killed was the least despicable thing Michael ever did.

Here Carlo is, this white trash on a free ride from the Corleones. To make things worse, he disrespects Connie in public and beats her. Also he cheats on her. And then the son of a bitch goes and hands Sonny over on a silver platter! He killed Michaels brother.

If I were in Michael's position, I would have killed the son of a bitch too! The way he waited so long was maybe a little cruel and unusual, but it had to be done. What we he supposed to do?