It's the Kindness Crest, the same one that Fluttershy has. Looks like a perfect fit for you.

[Donnie hadn't even noticed that Mikey was wearing his crest. He hesitated to answer the question, still not feeling like he deserved the Love Crest at all. Still, he had burdened Mikey enough and he couldn't make him hold onto it forever.]

Umm... y-yeah, I... I'm ready to take it back. [He held out his hand, for his brother to hand the crest back]