You'll be surprised as to how many people actually agreed with the ME3 ending. I can provide a link I came across very recently. It's scary really.
That's not the point. (I actually didn't mind the ME3 ending). The point is how angry/disappointed people will purposely tank review ratings on aggregation sites like Metacritic or retail sites like Amazon, using multiple accounts, even if they did/didn't purchase the game from that site. Amazon is pretty lenient on who can leave a product review, and their "verified" system is taking too long to come full circle.
Gamers can be very fickle and it's not the first time something like this has happened. Many people tried to tank GTA V's rating because they were pissed off about Heists being delayed for over a year. Others also tried to inflate & bolster the ratings of Destiny, in defense of a critically divisive game. Plus there are also instances of gamers assaulting reviews of books by authors who made disparaging comments about a game they love...even though they never purchased any of those books.
Just goes to show that the user scores should always be taken with a grain of salt since many (and in some cases, most) do not come from verified purchases.