Thomas the Tank Engine (Sharon Miller era and All Engines Go!)

Thomas the Tank Engine is an anthropomorphic train who is a major character in the British the titular protagonist of its TV series spin-off Thomas the Tank Engine and Friends. During seasons 8 - 16, he has become badly butchered. During seasons 13 - 16, he was voiced by Ben Small and Martin Sherman in the UK and US respectively.

Why He Lost His Charm
NOTE: This will only focus on how he was butchered badly back then.
 * 1) In Splish, Splash, Splosh!, he was being very uncareful while playing in the mud, therefore, his wheels would've rusted. Which proves the point his mischievous in it's worst in that episode.
 * 2) He has lost all of the personality and charm he had in the prior eight seasons and didn't get it back until season 17. He was turned into an engine from being optimistic, kind, cheeky, fussy, smart, and playful to being so darn happy all the time, hardly pays any attention or even listens to what the Fat Controller says, and so on and on in those dreaded seasons.
 * 3) In Wonky Whistle, he had a strange whistle sound that sounded really ear-piercing to the point that it scared away all the animals from a wagon he was pulling to a fun fair.
 * 4) Became extremely annoying.
 * 5) Overused a lot in seasons 13-16.
 * 6) Most of the episodes focused on him such as "Thomas and the Big Bang", "Wonky Whistle", "Percy the Snowman", "Up, Up, and Away", "Buzzy Bees", and so on and on prove that he is portrayed as an idiot, a clumsy simple minded character, and as well as an engine who screws everything up.
 * 7) Whenever there is a situation involved, he either makes things worse or messes it up until the things are set up right.
 * 8) In Misty Island Rescue he told Diesel he wasn't very useful because he was... well, a diesel. And he didn't get punished!

Redeeming Qualities

 * 1) He at least started to improve in season 17.
 * 2) He also wasn't as bad as how he did in Robot Chicken.
 * 3) There were episodes from the Miller era where he is in his best.