A. 
B. 
C. 
D. 
E. 
F. 
G. 
H. 
I. 
J. 
K. 
L. 
1) “I won’t tell you what my resolution is! I know you are all plotting against me!”
2) “My doujinshi will sell 3,000 copies at Comiket then get picked up by Weekly Shonen Sunday!”
3) “I will stop consuming people’s souls to fill the ever growing hollow feeling that I am not worthy of life. Also learn to cook western food better for sempai!”
4) “I could be nicer to those bandits.”
5) “This year I will try to let the love of my life get almost-raped less.”
6) “I will befriend everyone in the class and we will live together in harmony by taking out any punk that gets in my way using my newly improved supernatural abilities.”
7) None. He has no regrets that need resolutions to fix.
8) “I will set aside time from Mahjong each day to pursue my true passion: Needlework.”
9) “I’m going to win a fight all on my own this year. Seriously. For real this time.”
10) “I won’t buy the Fate/Extra Saber figure. I won’t, I won’t!”
11) “There will be more mecha anime this year even if I have to make it myself!”
12) “I will raise an ancient city with the power of my rock n’ roll this year. Oh, wait…”
Reverse Thieves 
Nice. I’ll take a crack at this, though I’m not familiar with a couple of the characters.
1 – C
2 – B
3 – umm…I?
4 – L…but she won’t
5 – A, but will most likely fail
6 – F?
7 – G of course
8 – K, and he will make it as extreme as possible
9 – D…no wait, that’s impossible
10 – E, too easy
11 – hmm…J
12 – H
Do we guess here? OK.
1) C
2) B
3) F
4) L
5) A
6) I
7) G
8) K
9) D
10) J
11) E
12) H
How did I do?
@kadian1364
So close. So very close. But you switched two.
– Hisui