The Cursed Seal of Earth had indeed given Anko a tremendous boost, and the side effects seemed remarkably manageable.
It wasn't that Orochimaru was unwilling to give her the Cursed Seal of Heaven, or the kind of cursed seal researched by fusing Jugo's cells as seen in the original timeline. Anko's natural talent was right there; one must be strong in oneself to forge iron, and in order to withstand the power of a stronger cursed seal, one needed the talent to properly wield it.
Therefore, after much consideration, Orochimaru ultimately gave her the Cursed Seal of Earth, formed by fusing cells of the Uzumaki clan. Anko already possessed formidable stamina, and coupled with an ample supply of Chakra, her endurance in battle would become even more extraordinary.
Chapter 122