When Anakin snuck up behind that assassin droid, he should have used the Force to slam him against the wall and be done with it. Engaging in hand-to-hand combat with a strong droid is about as stupid a tactical decision as you're going to get.
Stupid tactical decision no doubt but destroying a droid, an IG-88 assassin droid no less, with his bare hands was pretty damned impressive IMHO. I kind of thought that he was just trying to make sure it was *really* destroyed. While a simple force slam might work fine for most of the Separatist-created droids, I doubt that the IG-88 droids are quite as flimsy. He probably was concerned that if he didn't rip it to pieces that it might still be able to surprise attack him.