Dear Tineoidea,

He always tried to monopolize my time/attention and highly disliked it when I spent them on somebody else. He was also always critical of my other friends.
There was a project to which I invited him, that would then support my living. There he mostly alienated people with his reckless behavior and tried to defend himself when I told him to stop. He also kept making promises of helping me with this and that but never actually did anything I asked him of, even simple tasks, then complained about me “leaving him out of the decision making” when he himself barely engaged, had no idea about what was going on, encouraged me to drop the project and even went MIA for months.
So to say, the concept of personal accountability is mostly alien to him and he’s quick to anger.

Well, I have to say, with such friends, who needs enemies… His character is lousy, he is not just selfish and possessive, but unreliable and untrustworthy, and not taking responsibility for his actions, but accusing you of “leaving him out of the decision making”. He gets angry quickly, behaves recklessly, criticizes everybody else but has zero self-criticism and self-awareness.

He monopolizes your time, gets jealous and angry when you spend time with other people, accuses you of not spending even more time with him, and claims that he “was trying his hardest to be the best friend.” When in reality, he behaves nothing like a friend, but like a spoiled brat who only causes trouble.

What I felt though is that I had to erect barriers to fend off his possessive behavior. Yet I still cared a lot about his wellbeing and such.

You too, like your girlfriend, have a soft spot for him and gave him way too much leeway. You say you cared about his well-being. Does it mean you felt responsible for him, felt obliged to take care of him, in spite of his lousy character? Have you felt similarly obliged towards your family members perhaps?