1. Dozens of flats had been completely destroyed.

许多房屋被彻底毁坏了。

2. They're completely unmusical.

他们完全不懂音乐。

3. He's completely thoughtless.

他实在是欠缺考虑。

4. I'm completely disorganized.

我做事毫无条理可言。

5. Oh, I’m sorry. It completely slipped my mind.

噢，很抱歉。我完全忘了。