Is it bad/sinful for one to leave their parents coz they wouldn't allow their child freedom to live. Wouldn't allow them to do what they want to do wid their life (halaal way of course). And verbally abused em which caused the child mental stress?
If by "leave" you mean to abandon them then yes that is wrong because that involves cutting ties with relatives which is condemned in Islam. Prophet Muhammad (ﷺ) said, لا تحاسدوا ولا تباغضوا ولا تقاطعوا وكونوا عباد الله إخوانا (Nurse no grudge, nurse no aversion and do not sever ties of kinship and live like fellow-brothers as servants of Allah) - Sahih Muslim (2559). So do not abandon them or cut off ties with them. We were told by Allah (ﷻ) that families are often trials for us. Use this trial to come out victorious and strong, rather than to gain sin.
A great hadith for those in this situation where they are being mistreated by relatives:
Abu Huraira reported that a person said: Allah's Messenger, I have relatives with whom I try, to have close relationship, but they sever (this relation). I treat them well, but they treat me ill. I am sweet to them but they are harsh towards me. Upon this he (the Holy Prophet) said: If it is so as you say, then you in fact throw hot ashes (upon their faces) and there would always remain with you on behalf of Allah (an Angel to support you) who would keep you dominant over them so long as you adhere to this (path of righteousness). [Sahih Muslim (2558)].
That said, it's okay to get your own place. Just keep in touch with your parents.