It was extremely dark.

非常黑暗。

youdao

There was a dim light so we could all see better, but it was still extremely dark.

楼上昏黄的光下我们都看患上清楚一点，但照旧觉患上很是暗。

youdao

In this photo below, the water is extremely dark, and gives the feeling of being out in deep water ocean.

下面这张图上水的颜色非常深，看起来像在深海之上出游。

youdao

John Lloyd-Jones, representing Hinton, said his client had "extremely dark and disturbing fantasies".

BBC: John Hinton

Innovation is extremely frustrating, and I have no doubt that the ring leader of the Pittsburgh Six underwent many a dark night of the soul.

FORBES: The Pittsburgh Six: The Template for Innovation