Most Helpful Girl
I think that once respect, trust, communication, loyalty & etc.. once those factors no longer exist in a relationship between both parties no matter who does what to the other, and no matter how small or big the disagreements are the entire relationship becomes toxic for both individuals.
Most Helpful Guy
The biggest one I can think of is constant negativity. Looking at the cup half empty and always capitalizing on the bad instead of the good. Also selfishness, arrogance, and being controlling. Those are all very toxic