What is the worst monster in the 5.5e Monster Manual?

I've gathered the monsters that have received the most criticism in the 5.5e MM, and I want to answer the question: Which is truly the worst? Feel free to comment the reasons for your vote. P.S this is all RAW stat blocks, no homebrew tweaks. P.P.S. This isn't a critiscm of the MM itself. The fact that I have so little options so should speak that most of the monsters are very good.

I'd have to go with Werewolf, though not because of the lack of damage immunity. It's the way they handled becoming a lycanthrope. It's just awful.

What are the criteria for being "worst"? Are we talking "not up to it's CR", "worst to deal with as a player", "most complicated to run as a DM", or something else entirely? You mention criticism, but you could criticize the artwork and fall under that umbrella.

Worst could depend on several factors:

1. Monotonous or frustrating to play against.
2. Nonsensical abilities.
3. Mechanics don't fit with lore.
4. Is too weak or powerful for its CR.

I would say artwork doesn't count as I'm talking about the stat block, and as for the DM complexity, that's more a experience issue with the DM, unless it's really complicated, which none of the monsters in this book really are.

An example:

Werewolf could fit into 1, 2, or 3.

Noble Prodigy could fit into into 1 or 2.

Silver dragons could fit into 1 or 4.

Cloud Giant is pretty bad, two attacks per turn with no save incapacitated is pretty obnoxious.

Interesting! I hadn't considered any of the Giants because most of them were praised on first release.

The Cloud Giant definitely should be Incapacitated until the start of the creature's next turn. Makes it less evil and antifun, while still restricting a character's options.

Quote from Maruntoryx >>

The Cloud Giant definitely should be Incapacitated until the start of the creature's next turn. Makes it less evil and antifun, while still restricting a character's options.

 But that only denies the target a reaction. And I guess, gives advantage to other attackers. Otherwise, the target wasn’t going to do anything until the start of their turn, anyway.

I don't see what the issue is with the Cloud Giants. Most CR 9 monsters have 2-3 attacks per turn. And, the thundercloud does require a to hit roll by the giant. Admittedly, it is plus +12, but are there spells that require a to hit roll and gives the target a saving throw too?

And, I agree with Xalthu, the stunned until the end of the next turn is quite reasonable.

Quote from Siyaj_Kak >>

I don't see what the issue is with the Cloud Giants.

 Incapacitated, being action denial, is a very severe condition, so being able to do it twice per turn with no recharge is a problem (it's the same problem as a silver dragon, tbh -- silver dragon also has no cooldown incapacitate, just as an area effect instead of multiattack).

For both of them it's not that big a deal for a solitary monster, but it becomes a big deal when the monster is part of a group.

I think Cockatrice Regent is the absolute worst. Sure, you at least get a save, but at the level you normally encounter these bastards, Petrified pretty much means dead.
But I'll say Cloud Giant is a close second.

At least the Cloud Giant can only make two of those incapacitating attacks, and they are going to miss at least a small amount of them. I went with the Werewolf as the worst, because if a character gets cursed and NPC-ified at the level of the parties CR, it's still two levels away from getting Remove Curse, basically killing your character.