1. have an ax to grind
心怀叵测
如：she always has an ax to grind. you should take whatever she says with a pinch of salt.
她总是心怀叵测，对她说的话你得多留神 。
2.not have one’s heart in the right place
心术不正
如：he doesn’t have his heart in the right place. he would find every opportunity to stab in the back of others.
他的心术不正，动不动就在别人的背后捅刀子。
3. stab in the back
背后捅刀子
如：i was taken aback and didn’t think zhang would stab me in the back. i placed too much trust in her.
我万万没想到张某会在背后捅我一刀。我过去太信任她了。
4. badmouth somebody
说某人的坏话
如：i’ve never badmouthed anyone.
我从来没说过任何人的坏话。
5. beef
发牢骚
如：i’m really bored with his sitting there doing nothing but beefing.
他坐在那里什么事也不干，总是发牢骚，真烦死人。
6.speak with one’s tongue in one’s cheek
假惺惺的说
如：i feel sick of her. she always speaks with her tongue in her cheek.
我特别讨厌她。她说话总是假惺惺地。
7. smite with the tongue
血口喷人
如：don't offend her. she always smites with the tongue.
千万别得罪她，她经常血口喷人。