Can a Governor or the US President pardon an Assassin he hired?

Hello! I was scrolling along until I saw an article about a Pardon in Texas. In the comment section people talked about how pardons are even still a thing and one User pointed out that they are totally easy to abuse. Like why can't a governor hire a hitman to kill his political Opponents and then just pardon him? Would this be possible? Can a governor or let's say the president just straight up do that?

Thank you all in advance!