Momo

Momo is one of two ways to access the healing reflux debuff, the other being Awakened Seo Yoon. To note, healing reflux on an operator is far more accessible than healing reflux locked behind 6 DP and a team slot.

In PVE, Momo can one-shot “The Wall” C.O. enemy found on certain stages (i.e. Anastasia’s Supply Maintenance, Inhibitor Raid) because it buffs itself with a massive amount of health regeneration during its walling phase, which Momo just flips around with her Command skill trigger. This is more of a novel interaction than an enabler for new strategies. The alternative would be to engage with the game mechanics the way the developers intended. For reference, a Kim Hana raid comp will still one-shot an Inhibitor raid faster than one with Momo.

In PVP, Momo is a reactive operator meant to counter healing. Depending on the weekly meta, Momo can swing between good and totally useless. 

In theory, Momo can take advantage of any source of healing to inflict a massive HP% swing. In practice, it is incredibly difficult to justify bringing Momo over some other operator. Historically, Momo only sees widespread use on Rearm Chinatsu weeks.

It is important to keep in mind that sustain comes in the form of healing and shielding. Most comps will use a combination of the two to keep their units healthy. Momo does not “hard counter” sustain in the way her Command skill might suggest.