connective N2 common casualpolite

おまけに — on top of that

おまけに

Meaning

on top of that / to make matters worse / and besides — adds one more thing, usually piling onto an already extreme situation

道みちに迷まよって、おまけに雨あめまで降ふってきた。

I got lost, and to make things worse, it even started raining.

Attaches to	Form	Example
Sentence-initial (joining sentences)	[A]。おまけに、[B]。	風邪かぜをひいて、おまけに熱ねつも出でた。

残業ざんぎょうで疲つかれて、おまけに終電しゅうでんを逃のがした。

I was worn out from overtime, and on top of that I missed the last train.

この旅館りょかんは料理りょうりが豪華ごうかで、おまけに温泉おんせんまで付ついている。

This inn has lavish food, and to boot, there's a hot spring as well.

From おまけ ('a freebie / extra'). Frequently used for an accumulation of bad luck, though it works for a string of bonuses too. Spoken; in formal writing prefer その上 / さらに.

Jengo shows おまけに the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.

Sources Compiled with reference to A Dictionary of Intermediate Japanese Grammar.