Salam o alaikum. This hadith: "If anything could overcome The Decree then the evil eye would overcome it." Is this an authentic hadith? Thank you
Alaikumassalam wa rahmatullah,
The hadith you mentioned comes through two chains, neither of which is very strong. Therefore from my perspective it is not proven that the Prophet 
said that.
Ibn 'Abbas reported Allah's Messenger (ﷺ) as saying:
The influence of an evil eye is a fact; if anything would precede the destiny it would be the influence of an evil eye, and when you are asked to take bath (as a cure) from the influence of an evil eye, you should take bath.
Sahih Muslim 2188
Below is a diagram of the chains of the two hadiths that contain that statement:
Their combined authenticity is 16.5% according to the probabilistic verification method, which is far below the 30% needed for authentic hadiths. The hadith is not strong enough to be considered authentic, and not weak enough to be considered clearly fabricated. In everyday terms, the hadith is not strong enough to take into consideration.