The entire storyline revolving Kol's death is carelessly thought of.
- Elijah said, "no one hurts my family and lives": While we know that Elijah and Kol did not have the best relationship (Elijah had always seemed kind of indifferent to his little brother), the writers made Elijah look like a horrible person who didn't give a crap about anyone in his family being dead or in danger unless its Klaus, Bex, Hope, and Hayley.
- Elijah's apology to Elena about Jeremy's death, saying he knows what it's like to lose a brother was ridiculous (YES Elijah, you do know, considering she had a primary hand in BOTH your brothers deaths)
- Klaus said to Kol in TO season 2 that he *tried* to avenge his death: there is no reason why Klaus would not succeed! He is the most powerful supernatural creature in the world, he would have slaughtered everyone involved (and everybody they had ever met): but alas they cannot get rid of the MFG, so there was a major plot hole that made NO SENSE WHATSOEVER!!
Kol's death wasn't thought out, it would be far more realistic for the characters and their 'Always and Forever' crap to slaughter Elena, Jeremy, Damon etc, but the writers skipped that because they cannot kill the characters in TVD. So I just dismiss Kol AND Finn's death to being careless, stupid writing!
- Plus killing off Kol was out of character for both Jeremy and Elena, who kept insisting (and had other characters insisting) that they were good people - yet they were perfectly willing to kill off thousands of vampires they had never met just for their own personal gain, so Jeremy could complete his hunters mark and they could find the cure. Again, poor writing :/