Infernape is a good lead with good reason. It has a move for nearly every situation, and it has the stats and speed to take advantage of them. Steels and Tyranitar won't want to lead against Infernape. About the only thing that can stop lead Infernape is a faster psychic or Gengar. I would mention Weavile, but the only way Weavile hurts Infernape is if it is carrying Aerial Ace and even then, the OHKO is not guarenteed. In addition, if your lead Infernape has Mach punch, Weavile is no longer a problem.
If a faster psychic comes along, you can easily switch to a dark to absorb the psychic then counter back.