Four (Battle for BFDI 1-29)

Four is an integer and the main host as well as one of the three main antagonists (alongside Announcer and Purple Face) of BFB, and the non-canon one-episode series, Battle for Permission to Meet 10. Four and their co-host X first appeared in the 2008 video "X Finds Out His Value". They appear to be abstract beings representing real-life numbers, letters, or algebraic variables.

Why They Intentionally Were A True Blue Enemy Who Needs To EXIT

 * 1) To start of the list, they have basically became a ripoff of Chris McLean from Total Drama In fact, they have been very heavily flanderized when they've returned in Battle for BFDI (possibly even more so than Gelatin). In X Finds Out His Value, Four was a nice, caring number who cared about X and the other numbers, but in Battle For BFDI, they have a mysterious, sadistic, selfish and near-heartless personality where they use their powers to harm the contestants just for their own fun.
 * 2) They are a terrible host, for example, they abuse their contestants, and are even an abusive jerkass to their co-host X, despite showing compassion to them at times.
 * 3) Their voice is really annoying to listen to.
 * 4) They have absolutely little to no empathy for others. They don’t care about how others feel, as they often bully their friends for no good reason such as zapped Gelatin for stabbing them by accident in BFB 3 (even though he deserved it). He even mutilated Pin in BFB 1 and said "Pretty cool, don't you think?"
 * 5) * They are a psychopath, as they keep killing other characters for no reason at all and are just jerkass in general.
 * 6) They are also a Butt-Monkey (particularly in the later episodes), for example, the other contestants frequently treat them badly, such as yelling at them to revive the other contestants in BFB 2, and in BFB 16, the other contestants even left Four's show to go to Two's show. However, considering Four was rude and sociopathic to the other contestants, it's hard not to say Four deserved it.
 * 7) They went insane in BFB 30, where they transformed into objects and let them stay in the ground forever and to leave them alone.
 * 8) They were very immature & stubborn in BFB 16, where they refuse to get the EXIT contestants out and threw a tantrum for everyone switching.
 * 9) They sometimes go unpunished for their actions to the point where they're part of the Karma Houdini trope.
 * 10) They can't take criticism at all; for example, when Basketball called them pudgy, they got angry, and when Balloony & Lollipop High-Five, they got angry too and demanded them to do a High-Four.
 * 11) They, alongside Gelatin, take away the spotlight from the other characters.
 * 12) They treat most of their contestants like trash. Notable examples include Gelatin, Donut, Basketball, Balloony, Lollipop, Blocky, Taco, Black Hole, Clock, Loser, Profily & Gaty.

Redeeming Qualities

 * 1) They can be likable at times, especially when they returned in BFB 1, 4, 10, and 22. Also they are much more likable and tolerable in the non-canon shorts and at last they end up redeeming themselves in BFB 30, where they apologized for their cruel actions.
 * 2) They are at least nice to some contestants and sometimes X before their character development.
 * 3) To be fair, BFB would definitely not be as good as it is without them, since they are the hosts of the show and are involved in many of the episode's conflicts.
 * 4) Micheal Huang's voice acting for Four can be good to listen to, although that isn't saying much.
 * 5) "I, AM NEXT LEVEL, MAD."
 * 6) They get their comeuppance in BFB 6 as they ends up getting multiplied by A Better Name Than That and Zero (Donut).
 * 7) Being the mean-spirited, sociopathic, selfish and abusive villain they are, they were clearly supposed to be hated in these seasons as such.

Trivia

 * According to X, Four being a fan of BFDI as explains how Four was the "biggest fan" with him sitting in front of the TV watching the show, memorizing all the episodes, and telling X one day he would be famous.
 * After BFDIA, Four compressed all his show's recordings into one big block, thus creating the BFDI.