Last night I was playing in a MTT and there was one guy to my immediate left who no matter what I did would call me. This is fine when you have a hand as he pays you off but my question is, what do you do when you get something like AK or AQ preflop give a decent raise which he calls, you then miss the flop... Now what?

When someone keeps calling virtually every bet you make how do you place them on any particular hand?

I eventually lost most of my chips to this guy as I got pocket Kings and led out on every round with good bets as I wanted him out, he kept calling 1/2 pot+ bets until the A hits on the river and he re-raises, I called as I had so much commited anyway and he turned up A7

I know I should be pleased that people play like this as I will in the long run take his money off him but that doesn't ease my pain!

Commit less chips when you haven't made your hand yet and commit more chips when you do make your hand.
If there aren't a lot of limpers, you can just limp or min raise your AQ/AK and then bet hard if you hit, release with no worries if you don't.
With KK, push all in on the flop. If the calling station calls you with A7, there's nothing you can do. But if you just bet 1/2 the pot on every street, you are just begging him to keep chasing. If you want to slow him down, you gotta put all your chips in.

I concur with the above. It doesn't make sense to make big raises with drawing hands like AK, etc PF against a complete calling station (unless there are other players left to act you can knock out). Raise made hands like KK, and just keep firing pot sized bets . . . . But just check if you have a hand like AK and miss the flop. Don't hesistate to check it all the way down if you don't pick something up.

Ultimately, you have to pick up cards against the worst calling stations (who call anything). Long term you can wipe the floor with them, but realize that in the short run they can kick your ass (like sucking out an A on the river against KK).

Also realize that if they bet instead of just calling, you're usually beat. I think you could have safely folded KK on the river there given that he raised.

If you really decide you want them out of a hand, you have to push all in. But be warned . . . he might call against the odds and hit his hand.

Bet for value, Bet for Value, Bet for value. Don't bluff