Learn English – Idiom or phrase associated with a person who blame others for his or her fault

In English, a common term for such a person is "know-it-all", as in:

Ever since Bob took that first-year philosophy course, he's acting like such a know-it-all.

Usually the phrase has a slightly negative connotation to it, because it implies that the person really doesn't know it all, but they might act arrogant as if they do know it all.

I think you are referring to the choice between the:

lesser of two evils:

• the less bad thing of a pair of bad things.

  • I didn't like either politician, so I voted for the lesser of two evils. Given the options of going out with someone I don't like and staying home and watching a boring television program, I chose the lesser of the two evils and watched television.

(McGraw-Hill Dictionary of American Idioms and Phrasal Verbs)