expression
but I suppose; it seems; probably; I guess
Sentence-ending expression combining だろう (supposition) with に (contrary feeling). Often implies 'it would probably be the case, but...' or 'I suppose, though...'. Used when the speaker acknowledges a likely situation while expressing regret, sympathy, or mild contradiction.
彼ならできるだろうに、どうしてやらなかったんだろう。
He probably could have done it, so I wonder why he didn't.
もう少し早く出ていれば間に合っただろうに。
If you had left a little earlier, you probably would have made it in time.