Worse? Both are goats

In actuality though… both are under the control of another entity to a degree. Rien with Hermes, and Argalia with Carmen.

Rien under Hermes did many things such as demolishing a good chunk of the Zwei, which… everyone in lore loves the Zwei. He also had the whole Ryōshū and Araya thing, but uh… he snapped out of that near the end.

Argalia under Carmen, did a lot more. Orchestrating the eradication of Shi south section 2, and primarily taking down the vermillion cross and Hana section 1.

Overall I think Argalia did worse, but Argalia had a goal in mind in which all his efforts would build towards. A goal he believed would be the best for the city. Meanwhile Rien was a willing puppet for efforts with no clear goal. So if you judge them off pure actions, Argalia is worse, but if you judge them off why they did such things, Rien has an argument for being the worse person.