Cloud is unarguably one of the highest-tiered characters in Super Smash Bros for Wii U: he has a great neutral game, strong combos, and amazing kill potential. You can hardly go to a tournament without seeing one in the top 8.
However, you rarely see him actually emerge the victor at an event, and never at a major. TSM|ZeRo–who has a strong pocket Cloud–explains why this is. He discusses Cloud’s one glaring flaw–his recovery. Because he has weaker recovery than the rest of the top tiers, he is able to be gimped easily. An increasing amount of players are learning how to kill Cloud early, which makes his late tournament viability lower.
ZeRo does also extrapolate on why Cloud is not only strong in doubles, but almost necessary for any chance at winning an event.
Source: ZeRo