Celegorm, Curufin, and Caranthir are definitely the troublemakers and 'most guilty' of the sons of Fëanor. The twins never seem to do much of anything, and thus nothing particularly bad. Maglor and Maedhros both have redeeming qualities and are seen to struggle with the implications of the Oath.
The three middle brothers, though.....
I don't like to spend too much time figuring out which one is the worst - they all have some pretty serious downsides, and ranking them is just a question of which flaws you consider more serious.
Caranthir is the proudest, so he is unrepentently haughty. He says the types of things that make his older brothers facepalm, because that just kills diplomacy after he opens his mouth. He can't hide his scorn for the ugliness of the dwarves. He acts completely surprised that Haleth was able to fight off the orcs on her own. He's the one who makes the alliance with the Men who betray them. But, at the end of the day, he doesn't seem overly malicious - just bad-tempered from birth and not very good at making friends. His family puts up with him because they have to, but you don't see him winning friendships. There is the least change in him...possibly because he has less far to fall, but also just because he doesn't get progressively worse or anything. He was always that way, and the Oath didn't change that.
Curufin has his father's skill for oratory, but also a sense of ambition that is maybe not out of place in a younger son who has been denied leadership and realms of his own his whole life. He is the mastermind behind the kidnap-Luthien-and-take-over-Nargothrond plot. He is *way* out of line there, and very much leaves Finrod to die. There is a reason his son disowns him after that fiasco, and not just because it was plot convenient. Post 5th battle, he seems to be driving the Fëanorean decisions more than Maedhros. And he clearly knows Celegorm well enough to be the perfect accomplice.
Celegorm is strong and beautiful and can talk to every animal in existence. He would not be a candidate for the worst of his brothers, as he is more a person who reacts in the moment rather than plots out evil, except....except for that incident when he tried to force Lúthien to marry him. That's pretty egregious, and not surprising that Huan abandoned him at that point. There's also at least some indication that he was the brother who most wanted to attack Doriath to get the silmaril.
So...pick your poison with them.
The three middle brothers, though.....
I don't like to spend too much time figuring out which one is the worst - they all have some pretty serious downsides, and ranking them is just a question of which flaws you consider more serious.
Caranthir is the proudest, so he is unrepentently haughty. He says the types of things that make his older brothers facepalm, because that just kills diplomacy after he opens his mouth. He can't hide his scorn for the ugliness of the dwarves. He acts completely surprised that Haleth was able to fight off the orcs on her own. He's the one who makes the alliance with the Men who betray them. But, at the end of the day, he doesn't seem overly malicious - just bad-tempered from birth and not very good at making friends. His family puts up with him because they have to, but you don't see him winning friendships. There is the least change in him...possibly because he has less far to fall, but also just because he doesn't get progressively worse or anything. He was always that way, and the Oath didn't change that.
Curufin has his father's skill for oratory, but also a sense of ambition that is maybe not out of place in a younger son who has been denied leadership and realms of his own his whole life. He is the mastermind behind the kidnap-Luthien-and-take-over-Nargothrond plot. He is *way* out of line there, and very much leaves Finrod to die. There is a reason his son disowns him after that fiasco, and not just because it was plot convenient. Post 5th battle, he seems to be driving the Fëanorean decisions more than Maedhros. And he clearly knows Celegorm well enough to be the perfect accomplice.
Celegorm is strong and beautiful and can talk to every animal in existence. He would not be a candidate for the worst of his brothers, as he is more a person who reacts in the moment rather than plots out evil, except....except for that incident when he tried to force Lúthien to marry him. That's pretty egregious, and not surprising that Huan abandoned him at that point. There's also at least some indication that he was the brother who most wanted to attack Doriath to get the silmaril.
So...pick your poison with them.