in saying that he wanted “peace without victory,” president wilson demonstrated that he was a(n)realistidealisttough negotiatorcoward

I think that the best answer is realist: he knew that a peace with victory, that is a definite victory over Germany and its allies, would bring more bloodshed, then if either side were victorious, so he offered this, even though neither side would be satisfied.
In a certain way you could also argue that he was an idealist, that is that he believed that human life was worth more than a victory.

He was definitely not a coward.

I wouldn't call him a negotiator, as he addressed this to the US senate, but if this option were chosen, we would end up being one, as he'd need to negotiate such a peace with both sides.