Find your tribe in a Sea of Creativity
The 2012 version of TMNT is pretty well-known for not having the best characters' storyline endings. Timothy/Pulveriser, Fugitoid, and Alopex are the ones I have heard the most.
I'm curious to see which characters will have the most votes.
If I had to pick, I would say Timothy. He stayed as a frozen mutant even after Donatello found a cure. The Pulveriser may not be the best character but he deserved a happy ending.