Counterproductive, Phenomenon, Counterintuitive, Paradox, Conundrum
Adjective. Having the opposite effect to the one that was intended.
Noun. The outcome of some kind of unusual event, action, or process. Like the phenomenon of shopping mobs on Black Friday.
Adjective. When situations or results are contrary to what you expect.
Noun. When one person, thing, or action has two seemingly opposite characteristics. Also, making a decision that will result in both positive and negative results.
Noun. An unusual, complicated, and difficult problem. The solution could have several positive outcomes or several negative outcomes.