Of all the monster templates that are published, be by Paizo themselves or by 3rd parties, which one would you consider the most uncontrollable or that you can lose control pretty quickly with it?
For me [so far], the template that can lead to brokeness is the Undead Lord from Sword & Sorcery's Tome of Horrors Complete Unlimited Edition. Why? Basically, it's your typical enhanced undead template... until you read this part:
Create Spawn (Su): A creature slain by an undead lord rises in 1d4 minutes as an undead creature of the same type as the undead lord. Spawn are under control of the undead lord. This replaces any other create spawn ability the base creature possesses.
Applying it to a ghoul, a skeleton or zombie, no problem...
Applying it to a ravener... or a lich... or worst, such as Agmazar the Star Titan, y'know, ANY undead that can one-shot-kill an entire settlement? What would happen if an ravener undead lord wipes a village with its breath weapon? You would get a flock of raveners in no time. Ouch...
So yeah, while the Undead Lord is great for powering up weak undead, it's not so great for greater ones when they can turn every victim into their own powerful selves, under THEIR control.
First - Tome of Horrors is published by Frog God Games and Necromancer Games, not Sword & Sorcery (they did the Creature Collections).
Second, you're right, this could be a big problem. However, a Ravener destroying a town with its breath weapon is not a problem - you have to be a dragon in order to become a Ravener.
Third, the Create Spawn line should probably interpreted for each creature to only create spawn from those killed by its natural attacks (although I'd be cool with the breath weapon... Pseudodragon Ravener turning on a wizard...) - the template doesn't restrict it, because there are so many kinds of undead that it might not make sense for some.
Ehhh, Ravener and Lich aren't an issue sinc etheir Template has explicit restrictions on who qualifies.
I mean, still bad, since every dragon the Ravener kills becomes a Ravener, and every 11th+ level caster the Lich kills becomes a Lich, but not "Welp I killed a village now I have an army" bad.
Nono, what you want for THAT is the Dread Wraith Sovereign.
No limitations here.
Just roll into a random peasant village, kill everyone because their lack of magic weapons (or relative lack and the lack of anyone skilled enough to do jack to you) makes them helpless against you, and BAM!
Army of DREAD Wraiths.
Then they go out, and ravage the countryside, creating an army of regular wraiths while Mr. Sovereign create more Dreads.
It's the Shadowpocalypse on fast forward and 'roids.
Ehhh, Ravener and Lich aren't an issue sinc etheir Template has explicit restrictions on who qualifies.
I mean, still bad, since every dragon the Ravener kills becomes a Ravener, and every 11th+ level caster the Lich kills becomes a Lich, but not "Welp I killed a village now I have an army" bad.
Nono, what you want for THAT is the Dread Wraith Sovereign.
No limitations here.
Just roll into a random peasant village, kill everyone because their lack of magic weapons (or relative lack and the lack of anyone skilled enough to do jack to you) makes them helpless against you, and BAM!
Army of DREAD Wraiths.
Then they go out, and ravage the countryside, creating an army of regular wraiths while Mr. Sovereign create more Dreads.
It's the Shadowpocalypse on fast forward and 'roids.
Mother. Of. God.
Those ability score bonuses.
I vote for the tzitzimitl.
http://www.d20pfsrd.com/bestiary/monster-listings/undead/tzitzimitl
Ehhh, Ravener and Lich aren't an issue sinc etheir Template has explicit restrictions on who qualifies.
I mean, still bad, since every dragon the Ravener kills becomes a Ravener, and every 11th+ level caster the Lich kills becomes a Lich, but not "Welp I killed a village now I have an army" bad.
Nono, what you want for THAT is the Dread Wraith Sovereign.
No limitations here.
Just roll into a random peasant village, kill everyone because their lack of magic weapons (or relative lack and the lack of anyone skilled enough to do jack to you) makes them helpless against you, and BAM!
Army of DREAD Wraiths.
Then they go out, and ravage the countryside, creating an army of regular wraiths while Mr. Sovereign create more Dreads.
It's the Shadowpocalypse on fast forward and 'roids.
Mother. Of. God.
Those ability score bonuses.
Wow. Yeah. Nasty.
Although, the Dread Wraith Sovereign would really have to work at it to kill the peasants using CON drain or touch attacks, considering it has a 30' 2d6 cold aura. Most of it's victims would be dead from cold before it could kill them with drain attacks. But still, if it put it's mind to it, wow, that's one nasty-a$$ army!
How about the classic vampire template? In the hands of someone who'll actually use it to effect, like a PC?
Or worse, a DREAD VAMPIRE
The Skeleton Champion template results in a comically low. A Skeleton Champion Wizard 20 is CR 9.