Can a person still be bad after reaching enlightenment?

According to themselves - no.

According to others - yes.

Right and wrong, good and bad, are ways of experiencing reality. The human mind sees reality in terms of right, wrong, god, bad, therefore for humans everything is always either right or wrong, either good or bad. Everything is judged as something. Nothing just … is.

Enlightened ones don’t see reality in this way, they don’t perceive in those categories. They do not judge everything they experience. They do not judge.

As a result, in enlightenment there are no judgements. There is no good and no bad, no right and no wrong. Everything is.

That which humans consider good, is. That which humans consider bad, is.

Is. That’s all. Enlightened one is not good, and is not bad. Just is.