Sherlock is dead. John is convinced that Moriarty is involved.

He lures Jim to the flat and drugs him, ties him down to the bed and blindfolds him. He then proceeds to brutalize Jim, with Jim floating in and out of consciousness the entire time.

It wasn't until later that he realized that Moriarty actually had nothing to do with Sherlock's demise. John doesn't regret what happened.

Kinks can include - erotic asphyxiation, forced orgasm, gags, fucking machines, etc.