Mirai Nikki, Fate/stay night: Unlimited Blade Works Recommendations
Both animes are death games, where the last surviving player will win something on a mass scale. To survive the death games, the characters participating are given something to help them succeed. In UBW, the characters have servants, who were once heroic spirits, fend for them. However in Mirai Nikki, the characters have personalised future diaries .
Main characters in both animes have to play in survival game where the winner's wish will be fulfilled and the loser will face the death penalty
both animes are incredibly dark
Both consist of a competition to the death between several competitors to obtain some sort of power