Can compassion become toxic?

I had a toxic relationship (for the lack of a better word) with someone I thought was my friend and he manipulated my need to be compassionate towards him. It has made me overthink each time someone appeals to me for help. In retrospect, I was too proud to see the toxicity believing that I had the power to change him and his ways through love and support. After giving myself time and distance, I have realised that compassion, for the sake of reinforcing one's belief that one is compassionate, panders more to the ego than the soul.