If i sue my employer for firing me with no legit reason, is it possible they will sue me back or anything?

In the US you can be fired for any reason and any reason is a legit reason in the eyes of the law.

Even if they don't counter sue you can and probably will be made to pay all their legal fees when you lose.

They do not need a legit reason to fire you.  They do not need ANY reason to fire you.  You have no lawsuit, so they need no counter suit.

They cannot sue you without a valid reason.

anyone can file a law suit.  If they are truly in the wrong its unlikely they will waste money on a counter suit. However, if you are full s----t, they may countersue for expenses and libel.

Yes, but it is unlikely. 

In most places, your employer can fire you for any or no reason as long as it isn't discriminatory.  A woman was fired from my work, they had a legit reason, unfortunately multiple men had done the same and none of them were disciplined at all. So she sued for gender discrimination and got $40k. 

Is there a claim that they discriminated?

Employer doesn't need a reason for firing you, so any case will be thrown out and you will have to pick up your legal /court costs AND theirs

It's very possible.  It would be stupid, but stupid is possible.

Unless you have a contract your employer doesn’t need a reason to fire you 

Why are you suing