Android 17 was so powerful in Super for nearly the same reason that when Frieza and even Fat Buu trained they got a massive power boost.

Their base is already massive without any training.

Android 17 is organic and mechanical, so he has potential to increase his power through training.

Who stronger Android 17 or 18?

Even though her brother, 17, was mentioned to be programmed slightly stronger than her, he was unable to reach its maximum potential (Dr. Gero’s flaw, corrected on 18), making 18 the strongest of both twins. Akira Toriyama himself stated it during an interview (stament here ).

Why did Android 17 win?

Android 17 won the Tournament of Power for a reason, and it’s a reason many fans will not be able to argue against. When Goku was searching for strong fighters to represent Universe 7 in the Tournament of Power, his search brought him to Android 17 who had changed a lot since his time in Dragon Ball Z.