You went out with this guy a long time ago How do you make this person like you again because he hates you?
Apologise, if it's you that did something wrong, slowly begin to be friends with him, don't push him into anything and certainly don't ask him to forget everything that's happened unless he suggests it. As you talk more begin to flirt and try to regain his love or trust. Tell him you've missed him and eventually that you want to have him back. If you stick at it and it's 'meant to be' you should be fine (it may take a while though). If this doesn't work at all or is putting you through too much pain try to move on and find someone else. It all depends on how much he hates you though and for what reasons.