It's a tie between Bektic and Lewis.
Both faced opponents with technique and adequate physical ability, so it's unrealistic to expect them to dominate.
But Bektic fought at a good rhythm, was powerful, and well-rounded. He looked like a 145 lb Lombard with a worse chin.
As for Derrick Lewis, he was very powerful as well. It didn't take him much of an opening to finish May. And he created one out of a tough position. He's great at fighting out of them thru sheer will and explosiveness. He looked like a threat to just about anyone at HW.