Loki vs Sentinel Prime

While it's powered by the Mind Gem(I still can't believe no one believed me when I said that years ago), it seemed to be highly contained and used to hide it's energy signature.

Either Loki couldn't use it's full power because of the containment, or he didn't know about it. Either way from what I remember of the spear, it could be annoying, but I don't think it has enough power to seriously hurt Sentinel.

Also SP is voiced by Leonard Nimoy, which gives him extra powers.

His illusions would absolutely work on a transformer. If they can see, which they can, then it stands to reason you can alter what they are seeing. I've seen no proof his illusions wouldn't work. I'm not sure it means a win, but they would certainly work and aid in him winning or surviving.

His invisibility fooled the cameras in the Shield outpost during Thor's first movie.