Who is “right” then if everyone thinks they are “right”?

"If everyone thinks they are ‘right’ than who is ‘right’ that is why the Lord says that He weighs the hearts and we can test the spirit behind it." - G.S.MinsitrDef

Proverbs 21:2 (YLT)

Every way of a man [is] right in his own eyes, And Jehovah is pondering hearts.