Something pointed out by PointlessHub about Sentinel is that- "In his Transformers One video, Cody points out how Sentinel Prime was originally presented in the franchise as Optimus' predecessor, with little other characterisation beyond that. However, after Transformers: Animated introduced Sentinel as Optimus' smug rival, each iteration of the former has seen arrogance gradually become a defining character trait of his (even driving his motivations as the twist villain in Transformers: Dark of the Moon), further contrasting with his humble and noble successor. All of this culminates in the Sentinel we see in Transformers One; a proud, showboating, deceitful Transformer who betrayed the Primes for the sake of power and publicised himself as Cybetron's last Prime and sole saviour until the heroes expose him." That's what I find interesting is he went from a flat character to becoming more and more evil.
