He badly suffered cyberbullying himself. He realised the true dangers of social media only then.

A.  Such was his suffering of cyberbullying that he didn’t realise the true dangers of social media.

B. Only when he had realised the true dangers of social media did he badly suffer cyberbullying himself.

C.  But for his terrible suffering of cyberbullying, he wouldn’t realise the true dangers of social media.

D. Not until he had badly suffered cyberbullying himself did he realise the true dangers of social media.