What CR Should This Be?

[Alistaroc]

I fooled around with the stuff on the pathfinder SRD to make a creature that has low accuracy, solid damage, and butt-tons of HP. I want to throw it in to my game as a sort of mini-boss that will feel really satisfying to fight (one hit could kill you, it's all up to the dice, etc). But what should the CR be? Idk how to give it an XP value without CR.

Spoiler: Statistics

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Kudalamyek CR X
XP ???
N Colossal Construct
Init +0; Senses darkvision 120 ft.; Perception -4
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AC 10, touch 2, flat-footed 10 (+8 natural)
hp 124 (8d10+80)
Fort +2, Ref +2, Will -2
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Speed 20 ft.
Melee slam -3 (2d8+6)
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Str 10, Dex 10, Con -, Int 3, Wis 3, Cha 3
Base Atk +8; CMB +8; CMD 18
Feats Power Attack (-3/+6)
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The Kudalamkyek are colossal constructs that posess a
limited sentience that makes them popular in arenas. They
are manufactured only in Numeria, and the majority of them
find their way into Tymon for use in the gladiatorial
fights. Their high durability and destructive power,
coupled with their low intelligence and clumsy swings, make
them a crowd favorite.

Thank you

[Silva Stormrage]

On one hand thats a lot of HP and damage is decent but that is a really low to hit value. A single level 1 fighter could probably win the fight if he had an ac of 18 or higher.

I would probably say CR 2-3 tops.

[JNAProductions]

Ray of Stupidity would make this a very easy fight.

With a 95% chance to hit and 1d4+1 Int damage, you have a slightly over 70% chance of making this thing comatose with one standard action. If you prepared it twice, over the course of two turns you have a (.9025+.095*.75) 97% chance of shutting it down.

[Alistaroc]

On one hand thats a lot of HP and damage is decent but that is a really low to hit value. A single level 1 fighter could probably win the fight if he had an ac of 18 or higher.

I would probably say CR 2-3 tops.

Thank you!
I'm adding this to my table of potential door guardians. I have a new level 1 party trying to get out of a maze, but they'll be so worn down by the time they reach it I don't want them to go up against something that might just take them all out.

[aimlessPolymath]

Ray of Stupidity doesn't work- Constructs are immune to mind-affecting effects.

I would call this CR 2-3ish, yeah. The only way to take it down is by hitting it around 12 times, depending on class/build. It has what I might call a polarized matchup- it will crush pretty much anyone without medium/heavy armor and a 2H weapon, but anyone else is probably obliterated.
Note that average damage of its attacks is 15 without Power Attack, 21 with, which actually won't kill anyone outright, and some level 2 martials can take a hit and keep swinging.