Personally, I am not a very experienced OU player, more of a 2020 VGC player. However, I had a quick look over the list of gen 8 OU mons (Source is here! Please tell me if I am wrong)
When I first saw the question, know the phrase, "If you don't know what to do, just use Incineroar?
Well Reuniclus is gifted with a terrible defense stat, being a measly 75.
By having intimidate support, it could potentially increase it by 33% or: ~96 Base defense.
Not that I am trying to make it a mixed wall. However, it does get some niche tanks:
Also, I would change the EVs to:
132HP, 24 Def, 252sp.ATK+
Mainly because most mons in OU are physical attackers (Barreskwada, Cinderace, Rillaboom, MOST Dragapults, Conkeldurr, Bisharp, etc. etc.)
Some calcs with intimidate!!!
-1 252+ Atk Libero Cinderace U-turn vs. 132 HP / 124 Def Reuniclus: 86-104 (42.5 - 51.4%) -- 5.9% chance to 2HKO
Couldn't be bothered to change U-Turn into sucker punch. Same thing
-1 252+ Atk Choice Band Rillaboom Wood Hammer vs. 132 HP / 124 Def Reuniclus in Grassy Terrain: 153-181 (75.7 - 89.6%) -- guaranteed 2HKO after Grassy Terrain recovery
Tanks this Wood Hammer Rillaboom when:
252+ Atk Choice Band Rillaboom Wood Hammer vs. 132 HP / 124 Def Reuniclus in Grassy Terrain: 229-271 (113.3 - 134.1%) -- guaranteed OHKO
-1 252 Atk Life Orb Dragapult Phantom Force vs. 132 HP / 124 Def Reuniclus: 135-164 (66.8 - 81.1%) -- guaranteed 2HKO
252 Atk Life Orb Dragapult Phantom Force vs. 132 HP / 124 Def Reuniclus: 205-244 (101.4 - 120.7%) -- guaranteed OHKO
Those are just a few.
Onto the 'Intimidator':
Because Reuniclus is prone to Dark, Ghost and Bug, the obvious support mon to go for would be....
Arcanine is a nice alternative due to its speed and capability to snarl effectively.
However, Incineroar has much more bulk and can take out Ghosts with STAB:
0 Atk Incineroar Knock Off (97.5 BP) vs. 0 HP / 4 Def Dragapult: 156-186 (95.7 - 114.1%) -- 75% chance to OHKO
Additionally, Incineroar has access to Fake-Out, leaving those who are unprepared in for a flinch + a clean-up from Reuniclus.
So the optimal moveset for Incineroar is:
Incineroar ADAMANT Nature (I prefer this due to its offensive pressure. However, any other non-hindering is fine)
@Assault Vest (to be a mixed wall) OR: Sitrus Berry (Because who doesn't love a tasty fruit?)
EVS: 232 HP, 56 Attack, 200 defense, 20 speed. ------ 20 speed is to outspeed most other 60 base speed mons (which is a LOT), not 4 because that is too common, 200 in defense because more than Half of OU are all physical sweepers, chuck 232 in HP because it will become a 2HKO or 3HKO rather than a OHKO, 56 in Attack to threaten Dragapult (Also gotta remember Dragapult will most likely go for Phantom Force turn 1).
Flare Blitz ------ Stab and for annoying threats like Rillaboom, Amoongus, Ferrethorn, Copperjah, Darmanitan
Darkest Lariat/Throat Chop ------ Depends. Because of dynamax, mons can boost their defense regularly/Corviknight using Iron defense. Darkest Lariat will ignore this (Though the main reason why you use it over Throat Chop is because of its extra 5 BP. Throat chop to stop Hyper Voice Spammers -- I'm looking at you Primarina and Sylveon).
Fake out - Duh
Parting Shot/Close Combat------ Parting Shot is optimal. However, I like close combat because of the shocked faces against other Incineroars ****That's funny.
More or less, Incineroar for its fake out, menacing offensive possibilities and Intimidate. Not too sure if you will agree. However, nothing can go too wrong with Incineroar.