If you say that someone is ruthless, you mean that you disapprove of them because they are very harsh or cruel, and will do anything that is necessary to achieve what they want.
The president was ruthless in dealing with any hint of internal political dissent.
这位总统对任何内部政治分歧的苗头都毫不留情。
A ruthless action or activity is done forcefully and thoroughly, without much concern for its effects on other people.
Her lawyers have been ruthless in thrashing out a divorce settlement.
她的律师们在协商离婚协议上毫不留情。