Betrayal

throw under the bus

Meaning: to betray a partner, colleague or close friend for self-benefits

Example: Mark always looks for someone to blame and throw under the bus for his failings. Read on

sell someone out

Meaning: to betray someone

Example: The company had put a lot of trust on him, but he sold them out by leaking confidential information to the competitors. Read on

viper in bosom

Meaning: a person who deceives you after receiving help from you

Example: I got my friend a good position in my company and all he did is convinced my manager to get him the designation I had in the project. He was no more than a viper in my bosom. Read on

show true colors

Meaning: to reveal what one is really like

Example: I trusted her blindly, but when I was in need too much and called her for help, she showed her true colors. Read on

stab in the back

Meaning: a disloyalty

Example: I have done everything for her, but she left me because of that guy, she stabbed in my back. Read on