You do realice that the one making a positive claim is you, not me, right? The burden of proof is on you, not me, to prove that Gaara killed shinobi from other villages illegally.
His killings during his childhood were Shukaku not him. It's specifically shown in the manga how he would be horrified when he gained control again. He was involved in the plot. Yes, he was. He was obeying orders from the Kazekage. EVERYBODY FROM SUNA WAS INVOLVED. It was a war, a direct order from the Kazekage.
He absorbed him to save his own skin. Again, broken window. And he brought him back as well.
He didn't help? His express mission was to destroy Konoha. You know, his home village? He fought Black Zetsu, yes. Not really something to be proud of, since it wasn't for the purpose of helping the Shinobi Alliance. Itachi, well, we found out the truth later on, so killing him is nothing to be proud of. Kabuto, again, broken window. He didn't want to help the Shinobi Alliance. He just wanted to talk with Itachi, who told him he would after he'd beaten Kabuto.
And, like I admitted, Gaara's crimes amount to killing a few Suna shinobi and a few other shinobi during the Chuunin exams. Both are morally wrong, but they're not illegal. He gained Suna's trust, and the shinobi he killed during the Chuunin exams were fair game.