So I’ve been thinking about stuff, specifically Soundwave, and I think I’ve come to a conclusion. I don’t think that Soundwave is actually “evil”, per se, not in the way that you would consider Starscream or Airachnid or the other Decepticons to be. I think he’s just a sort of fanatical follower Megatron.
My main reasoning is that I don’t recall him ever hurting anyone except to directly protect Megatron (see: kicking Airachnid’s ass in episode 26). He might have fought with someone, and yes, he did kidnap Agent Fowler, but he has never tried to kill someone. Not even the kids, in spite of the fact that he had a perfect opportunity to. They had no protection, no Autobots to cover them. Starscream probably would have. Airachnid definitely would have. Soundwave didn’t.
Instead, I think that Soundwave has his own morals. He apparently isn’t above kidnapping or doing pretty much anything that he is ordered to do, but if he isn’t under orders, he won’t kill. I think he’s probably a lot more idealistic about Megatron and his plans than the other Decepticons, and that is why he stays so loyal to Megatron alone while the others err on the side of whoever seems most powerful at the time. (Knockout, for example, is willing to side with Starscream while Megatron is in stasis, but once he wakes up, Knockout is totally loyal to Megatron again.) Some, like Starscream and Airachnid, even try to grasp power for themselves. But not Soundwave.
I like how TFP!Soundwave can be pretty ambiguous.