Abuse Cycle is one of those things you should read just because of the impact it will have on the fanbase. It's pretty similar to the infamous Ranma 1/2 darkfic, "The Bitter End."
That is to say, Abuse Cycle takes all of Mako's nasty habits and extends them to a rather unfortunate conclusion. I say read the thing if you can stomach a darkfic, it's pretty well written all things considered. Abuse Cycle seems to be Lo K
fan history in the making, for better or worse. Just keep in mind that Mako is probably not going to start smacking Korra up in canon any time soon.