Most useless screen time: Jolt.
Jolt took what could have been one of the best Ratchet scenes ever in
TF history and made Ratchet even more useless in the movieverse. A close up of ratchet working on Prime, adding Jetfire's part to him would have rocked so hard. They could have just shown him start to combination/medic process, then jumped ahead to Prime beginning to stand up as Ratchet finished the final details. Then have Prime jet off to fight the Fallen. But instead we get a forced robot using two electric whips to somehow make a Super-Powered Prime. UGH.
Most under-used Autobot in the films: Ratchet. Without a doubt.
Ratchet obviously put Bumblebee's legs back on after
TF1. And he is stated as the medical officer, but we never see him actually do his job (outside shooting a "plasma beam" into BB's throat). He had more missed opportunities in both movies than any other Autobot IMO.