killing that bird was definetly gruesome!
But not just that, he was also handled well and had a lot of cool scene. I'll go with him.
I liked Soundwave also and Shockwave was looking great with his "machine", he really seemed to be a real threat, but not as I expected. He didn't do much... The same with Megatron, he didn't do much, even though I loved when he kicked Sentinel's ass in the end, before Optimus killed both.
Usually I love Starscream, but he appeared weak (again!), add to the fact that he didn't had much screen time. The most disappointing Decepticon in this movie, the only scene with him that I loved was when he destroyed the ship of the Autobots, but that was pretty much it.