stress is good for literally nothing at all and tends to fuck you over.

So far, i've regret 99% of all the decisions ive made here on earth and it makes me really sad, so i have to go with regret

apathy, towards everything makes life boring as shit

Some scientific studies on responses to different emotions seem to indicate that humiliation gives humans the harshest negative reaction. I would just on intuition agree with this.
People in certain cultures have literally committed ritual suicides to avoid or cleanse humiliation.
While ritual suicide seems like a harsh reaction to humiliation, in cases of suicides especially among children/teens, there very often is a component of bullying/humiliating of the suicide victim.

This would make sense to me at least.

I've gotten a lot of really good answers here, I'm enjoying the opinions, keep em coming.

I think generally speaking feelings of vengeance or anger are worst ones.

They make you do irrational things that you otherwise wouldn't see the need to do, and that never leads to good outcomes. If we didn't have these emotions the world would be so much better.

For me personally it's jealousy.

It's easy to get jelous over something you didn't experience or don't have if you trully care for that thing.

Jealousy works differently for everyone, but it can cause anger and sadness which fall into even more categories like alchoholism, suidical thoughts, depression, stress, fear and so on, like I said it works differently for everyone, and it depends on what it is that you're jelous of.

It can make you change as a person too, your character and the way you live on the day to day basis.

Other than the ones that have been said already, anxiety.
Especially if you get anxious over every little thing very easily. Anxiety paired with stress is the worst.

I'd say love, if you think seriously about the love, it can make you happy and accepted in some cases but, you can get really sad and afraid thinking about losing it, failing on love por simply thinking in not find love, and if your love isn't accepted you're gonna get angry and jealously of the other people that found love, making you in that case in a toxic person that hates temporally the love

I'd like to say hope.
Cause hope can drive a man insane

And hope destroys life