2 sentences for 用心 (yòng​xīn — motive)

1. 他这么做显然是别有用心。

   tā zhè​me zuò xiǎn​rán shì bié​yǒu yòng​xīn.

   He clearly has ulterior motives for doing this.

   Source: Dong Chinese Dictionary

2. 他的用心险恶，企图挑拨我们的关系。

   tā de yòng​xīn xiǎn'è, qǐ​tú tiǎo​bō wǒ​men de guān​xi.

   His intentions are sinister, as he is attempting to drive a wedge between us.

   Source: Dong Chinese Dictionary