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
"The Grand Admiral was smart and subtle, but never used his brilliance to show up or humiliate anyone.
He demanded results, but never perfection, and had amazing stores of patience for those who were truly working to their fullest ability.
It was a pity Thrawn's style of leadership hadn't spread through the rest of the navy.
If that happened, he suspected, the Empire would stand forever."
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.