Political online game and economic simulation

I heard that if you have a negative reputation you even as a classic state can get attacked by a foreign power, computer state? Though, I have a very postive reputation, just asking! And how powerful ca the state be, if you are the most powerful state, then would it attack with the most powerful computer state? I know its a rare exitus!

That can happen if your international rep is very low in the negatives. Indeed it's rare, but it can happen. When that does, you simply get a message - informing you that your regent's country got invaded. No need to worry, so long as you stay on the right side of 0 vis-a-vis international rep.

Can you beat it if you are very powerful military wise, and if you have your alliance? And can other countries stop it if it attacks?

It's just a scripted event. I don't know if it can happen to a state with a very powerful military index.

States with a bigger military are safer. Military assistance from an alliance is also counted in, from what I know.