认为: think 认定: very sure 100%

认为is like your opinion, you can认为something is right while it isn't 认定sounds you firmly believe something and experts can 认定 the truth, which is more authoritative

认定是认为的加强版， 认定的语气比认为更重。 认为:认识到为这样， 认定:认识到一定这样。