Tate no Yuusha no Nariagari is good, even though we haven't gotten to the part where the mc becomes OP.
Alice in Hell has quite a cold hearted, strongish MC, and the story is interesting. (has not been updated for a while)
And obviously Tower of God, even though it can't be uploaded onto this site anymore ;-;
Edit: Also, Until Death Do Us Part.
Edited by omnipwnage, 23 September 2014 - 03:37 PM.