moreover; in addition, on top of it; above it
And on top of that, if you went blind, it would be a complete tragedy.
— ラストエンペラー (1987)
It was starting to get dark, and to make matters worse, it began to rain.
To die so young—and on top of that, if anything were to happen to my son…
— ラブ・アクチュアリー (2003)