Quite a lot of people who survived a suicide attempt (especially by jumping off bridges) tell how they regretted their decision the same moment they jumped

After a successful hanging, there are plenty of possible afterlife scenarios where you could have plenty of opportunity for regret. Most religions teach that suicide is punished in the next life. If we're living in a physics experiment or computer simulation, there's no guarantee our consciousness won't be stored elsewhere after death, opening up the possibility of regret, especially of the storage system sucks.

Maybe there won't be an opportunity for regret, but it's certainly not definitive.

This depends greatly on your philosophical belief of whether you will ever be held accountable for all your actions, good or bad, after you "cease to exist".

As if death by hanging is an instantaneous atomic act, you're very likely conscious for some time both during and after the irreversible moments.

This naive view is why for centuries we haven't seen any improvement in the happiness of ghosts.