10. Ben Solo
Ben Solo - or as he is better known, Kylo Ren - is without a doubt a fantastic character. His introduction to the sequel trilogy brought something fresh and dynamic. You could sense the crushing amount of pressure that he felt from being a son of Leia Skywalker and Han Solo, plus he embodied the conflict of the Dark and Light side of The Force in a gripping way. Despite this, he falls right down here, as he spent the majority of his time on the Dark Side.
As a character, he's excellent, but there is very little to note of him as a Jedi, and he only slips in by default. You see precious little of his early days in training with Luke besides the infamous scene that saw him almost slain by the legendary hero. As we all know, he would end up turning to the Dark Side because of this, destroying all hope for the Jedi - for some time at least.
He did find redemption at the climax of Rise of Skywalker, but his new life as a Jedi was cut short. Plus, his general transition from villain to hero felt sudden and rushed. Of course, everyone is capable of change, but Ben may have gone too far.