Eöl

[Kuruharan]

I think that's usually what happens when you answer a polite greeting from a King disrespectfully and then kill his sister.

Well, that second one was sort of an accident, but your point is taken.

Probably the act that weighs most heavily against Eöl is his attempted killing of Maeglin. (Although, was this really a bad thing?)

Eöl likely felt betrayed and humiliated by what had happened. There was an open rift between Maeglin and Eöl before they split, but the text makes no mention of Aredhel ever mentioning her thoughts on the matter to Eöl. (Not that he would have agreed with her considering his orders not to consort with the Noldor, but still…) The text also makes no mention of Eöl’s reaction when he learned Aredhel was dead. (I suppose it is remotely possible he was not told, since she did not die until after Eöl was in the clink.) However, that Aredhel begged Turgon for mercy even after Eöl had tried to kill her son indicates that she still loved him to some extent.

As Lalwendë indicated, Eöl’s actions there were of someone driven to desperation by the loss of everything he held dear.

I am strongly reminded of Denethor.