Why go after Leiter?
First of all Sanchez was in the United States and on the run, it seems like having Leiter whacked was a huge risk, secondly why just him? Why not anyone else who assisted in his arrest? I get that he wanted to intimidate anyone else who might try to bring him to justice but it just seemed like a huge risk and not a very big pay off.
Also am I correct that Killifer told Sanchez that Leiter was the one who busted him? Why didn't he tell Sanchez about Bond as well?
Also why didn't they make sure that Leiter was dead? I mean sure he couldn't ID the warehouse but he could ID Krest and the two aquarium guards, that could get Krest busted which would hurt Sanchez's business. Plus he almost certainly told the cops that Killifer was crooked which means he can now no longer set foot in the United States ever again (well Bond fed him to the shark so I guess that's nothing he has to worry about, but this was before that).