Vector Prime, Animated Starscream for good, Yoketron, Animated Prowl, RoTF Jetfire. Do I need to continue? Can we not talk about death since some of us are still mourning the deaths of certain characters in a certain epic show?
My only problem with resurrection of characters comes from the Unicron Trilogy. I loved the shock and awe of Smokescreen's death in Armada, it would have been a great end for a mediocre character, but no! He's back in 2 seconds as Hoist. :/ Same with Demolishor. Demolishor was one of the better characters from Armada/Energon and his death was amazing! It was so senseless, and sudden. That's great drama! Nope, he's back as a dump truck without any of the character development previously established. Ugh. Also...Why bring Inferno back? So dumb.
In a way sparks have made it far too easy to bring 'dead' characters back to life. This weird ball of energy whose properties and limitations are never really clarified means that an entire TF body can be obliterated and yet the character still come back. Even when the spark was completely gone in the case of BW Optimus Primal after the transwarp explosion his spark was still able to be retrieved from 'the other side' and put into a new body. It's even easier if a TF's spark is saved around or after the time of death. Even without the clone thing of Dinobot 2 in BW I'm sure if the writers had wanted to bring the proper Dinobot back they could've easily just come up with an excuse for his original spark to have been able to be restored. At least back when they were just sentient living robots being destroyed meant actual death was more likely because the death was more mechanical and less 'spiritual'. But then they're machines so extents of damage the possibility of being repaired is always going to be an easy out for bringing back an expired character.
If you're gonna talk about the Unicron trilogy. One particular character that died and stayed that way was Thrust. Being ground up in Unicron's gears until your head popped, now way he could come back.
As long as there return makes sence then fine. But someone like dinobot who had a hero's death it kinda ruins the emotional impact of that death for returning him. It be like if tony montanna got medical treatment at the end of scarface and was able to live.