Very likely voiced by one. It's common for little kids to be voiced by female actors to sound more childlike.

Same voice actress than Shinji from Evangelion 😅

昔から日本はくさってるみたいだよ 赤尾敏さんみたいな人が居ないと駄目 日本国民への生活支援して欲しい！！ 政府マジでダメ深刻！！ 政府マジでダメ申告！！

You mean the one attacked by 2 Drag Slave? No, that's Fribrizo, the most powerful of Shabranigdu's subordinates. Xellos woul've been killed by that double drag slave, considering a far more powerful mazoku like Fibrizo was overwhelmed by it enough that he had to move to another dimention to avoid being harmed. Remember, he destroyed Gaav with a snap of his fingers, the same Gaav that stomped Xellos. Yeah, he was injured after taking a Ragna blade to his body, but considering that a complete, not sealed (like we see in the anime) Gaav is still weaker than Fibrizo, the gap between Xellos and Hellmaster is considerable. Something like this: Fibrizo> Gaav >>> sealed Gaav>>>Xellos.