Hit-or-miss; the chance that something will be a success or failure, or variation in quality/returns (e.g., lottery, gacha, products).
この店のランチは当たり外れが大きいので、運が必要だ。
The lunch at this restaurant is hit-or-miss, so you need some luck.
ガチャは当たり外れが激しいから、注意して回した方がいい。
Gacha capsules are very hit-or-miss, so it's better to spend cautiously.
期待した映画だったが、評判どおりの当たり外れがある作品だった。
It was a movie I had high hopes for, but it turned out to be a film with mixed results, as reviews suggested.