Sonic Lost World 3DS is one of the worst Sonic games I've ever played, but somehow, it makes you come back for more of its questionable level design, and often tedious gameplay. And this is very clear when it comes to Frozen Factory Act 3. As if the game didn't already have questionable gameplay/ level design, this stage takes that to another level, and here's why.
1. The Snowball gimmick.
The first reason why this is the worst Sonic stage known to mankind is because of the snowball gimmick. Basically, it's where you have to move a snowball to a switch, which will activate a box with a portal, item, rings, etc. This completely destroys the pace of the stage, as it takes a long time to just get the snowball to the switch. It pretty much forgets the speed aspect of Sonic. While Act 1 has this, it's not nearly as bad as here.
2. The Chasing Snowman.
The next reason why this stage sucks is because of this chasing snowman thing. This is basically where a snowman chases you, and if it hits you, you become frozen temporarily, and the only way for it to stop is by stunning it, then homing attacking it. While you could say this is a good way to add speed to the stage, it isn't. This is because when the snowman chases you, you already have to take your time, but that's impossible here.
3. The Gameplay.
The final/big reason as to why this stage is crap is because of the gameplay. While this game already has some slow, Mario-like gameplay, this stage takes it to another level. This stage's gameplay is so alien to what Sonic is, and feels like a stage from Super Mario 3D Land or something. While you can say the same about Labryinth Zone, at least it didn't have any gimmicks that make it feel different from a Sonic game.
Conclusion.
In conclusion, Frozen Factory Act 3 from Sonic Lost World 3DS is a menace to society is because of its tedious gimmicks and gameplay, along with its gameplay that is extremely alien to Sonic. In my opinion, this is worst Sonic stage ever made.