What win rate does a profitable strategy need?

None in particular — win rate is meaningless without the payoff ratio. A strategy winning 35% of the time is comfortably profitable if winners average 3× the losers (expectancy = 0.35×3 − 0.65×1 = +0.40 per unit risked); a strategy winning 70% of the time loses money if occasional losers are 4× the winners.

The break-even formula is win_rate ≥ 1/(1+R), where R is the average win/loss ratio. Trend-following systems typically live at 30–45% win rates with big winners; mean-reversion systems at 60–80% with small ones. Judge the pair, never the win rate alone.