I'm not sure what exactly qualifies as a Android, but Anilaza just in Dragonball Super I would consider more powerful then 17. Go outside and we have DC androids like A.M.A.Z.O and Hourman 1 million (?). So I wouldn't say he is the most powerful in fiction, I'm also positive some exist that I know nothing about.
Peak versions of Amazo can copy/attain infinite power(literally)... So I'd say him.
...Unless Thought-Robot counts. /shrug
"This bold vision of the future requires a vast military dedicated to upholding the enactment of universal laws which are necessary to ensure galactic harmony.
In truth, these actions are taken merely to protect us from those who would invade, enslave, or foment political dissent, and to punish accordingly any who engage in such acts.
Look on our new military not as trespassers or interlopers, but as gatekeepers, here to shore up the Emperor's vision of a pacified and prosperous galaxy."
If Cell had the chance to train while being alive again, pretty sure his potential would outclass 17 getting stronger through training with animals or whatever he did as a ranger, but 17 still a cool guy now regardless.
Thought Robot? Suppose ya got me there. I first saw Amazo in the JL cartoons, but was disappointed when I looked at most of his comic versions in comparison.