Mercenaries 2: World in Flames

Easiest place to earn this achievement is the back of the mansion. There are a bunch of potted plants, tables, chairs, etc. by a pool, walk up to an object, press B and your character will melee it. Repeat this 49 more times and the achievement is yours. Took me about 4 minutes max. 10 objects a minute.

On a sidenote to Lodoss Inderos's guide, destroying something using melee also works on enemies. So, as another way, as you go through the campaign, just beat down on as many soldiers as possible to make progress in the game, as well as nabbing yourself the 'cheevo.