(simply) because; on account of — used to emphasize a cause that led to an undesirable result (often expressing regret)
電車が遅れたばかりに、会議に遅刻してしまった。
Because the train was late, I ended up being late for the meeting.
うっかりミスをしたばかりに、信用を失ってしまった。
Because of a careless mistake, I lost credibility.
お金がないばかりに、留学を諦めた。
I gave up studying abroad simply because I had no money.
as if to; (as though) about to — used in expressions meaning 'almost' or 'on the verge of' (e.g. 'as if about to cry')
彼女は泣かんばかりに目を赤くしていた。
She had red eyes as if about to cry.
驚いて倒れんばかりにのけぞった。
He recoiled as if about to faint from surprise.
合格を知らされて、彼は飛び上がらんばかりに喜んだ。
When he was told he passed, he was almost overjoyed enough to jump up.