General negativity:
* Dreadful: Extremely unpleasant or bad.
* Awful: Extremely unpleasant or bad.
* Terrible: Very bad or unpleasant.
* Appalling: Shocking and unacceptable.
* Abominable: Extremely unpleasant or repulsive.
* Despicable: Worthy of hatred and contempt.
Meanness and cruelty:
* Vicious: Cruel and violent.
* Malevolent: Wishing harm to others.
* Ruthless: Having or showing no pity or mercy.
* Sadistic: Deriving pleasure from inflicting pain on others.
* Brutal: Extremely cruel and violent.
* Savage: Fiercely cruel or violent.
Other synonyms:
* Deplorable: Extremely bad or unacceptable.
* Reprehensible: Deserving strong criticism or censure.
* Heinous: Extremely wicked or evil.
* Outrageous: Shockingly bad or unreasonable.
The best word to use depends on the specific context and the nuance you want to convey.