The only way to win with a toxic person is not to play. Leave their "playground".

The attitude of "that's just how I am, take it or leave it" is still a sign of immaturity. As an adult, it's your responsibility to figure out which of your traits are toxic and are negatively impactful towards other people and the ones you love, and to eventually learn how to fix them. At some point, we all gotta start making ourselves better individuals. If you truly believe you don't have to change anything about yourself, even at the very least the worst in you, still a child.