A/N: this is sort of a guess from me on how strong android 21 might be. I'm only going to go by some suggestions.

Now she's has been stated be be strong enough to compete with the series strongest of fighters. While it doesn't specify on that, my bests guess are that's she's at least possibly stronger Tournament of Power Saga Goku at Super Saiyan Blue.

While being a bit weaker or around beerus level.

Not only that, but she may actually somehow have a Transformation.

(If you look closely at the person with the red aura, their hair looks just like android 21's but white. Could it be that she somehow got a Transformation state? If so, it could raise her power even higher than I thought).

But that's just me. If you guys have any guesses on how strong she may be, leave a comment. And once Dragon Ball FighterZ comes out next month, all the questions will be answered.