Guild Wars 2

You get rewarded. A melee hero can not do this though since you have to circle kite with range

Playing from a thief perspective, while levelling, I could consistently underlevel kill things. I did this because I would quickly get bored with an area and go after skill points in the next higher area. In the 30s and 40s killing things 5-8 levels higher wasn’t to bad, but as I got into the 50s and beyond, this level gap kept narrowing and narrowing.

Just letting you know what to expect. Now at 55 I don’t like fighting anything more than 4 levels higher, and I try to avoid even that.

You get a 10% bonus to magic find for every level above you that the mob is.

Quite easy to kill stuff 9 levels above you. 10 levels is where it gets too painful. At a 10 level difference they gain complete immunity to all conditions you try to inflict. And condition damage is the way to go for killing stuff many levels higher than you. (It still does full damage because condition damage either lands or doesn’t… there is no scratch damage for conditions.)