In general, the Hypostasis is quite easy to beat, so players can use single characters to beat them (I do this all the time with just Tartaglia). It is recommended to use a high DPS character along with the ability to do a few ranged attacks. I would recommend using Tartaglia if you have him since he can do both ranged and melee attacks. I use Tartaglia to clear out almost all of the bosses, he works well against Signora, the Pyro Regisvine, and the Pyro Hypostasis as well. Kaeya and Xiangling are excellent free-to-play friendly options if you are fully focused on tackling the Anemo Hypostasis alone. Other characters that can excel at solo attempts would include Ganyu, Hu Tao, Diluc, Raiden Shogun, Arataki Itto, Kamisato Ayaka, Keqing, and even Eula.