can't possibly win, have no chance of winning
勝てっこないさ。
There’s no way we can win.
どうせ勝てっこないよ。
There's no way we'll win anyway.
絶対、勝てっこないって。
There's absolutely no way we can win.
やらなきゃ勝てっこないよ。
If you don't do it, there's no way you'll win.