My nod goes to the 24 team for leaving Byron out too long on the last green flag stop. Had the dominate car and managed to lose the race.
I would think that Brad Keselowski's crew gets an honorable mention. They probably at least had a top 5 car, possibly a winning car, and threw it away with a bad pit stop or loose lug nut.
Byron's team gets an honorable mention as stated in the original post by @MRM
But I think Larson clearly takes it hands down. They should have parked it with about 50 laps to go. The late caution was a terrible thing and unnecessary.