Exactly, that's why supporting Ukraine is extremely important. As long as the aggressor still thinks there's a chance to conquer more territory, the war won't end.
I would say that the US also belongs in the agressor camp.
Do you mean globally in general? They're obviously not the aggressor in Ukraine. My Ukrainian friends didn't have their their family home annihilated US shells directly or indirectly.
Whether you are an agressor or not depends on the conflict. One can be both in different conflicts, and even change roles over time in the same conflict.
Yes, and in the Russian-Ukranian war Russia is the aggressor.