Here's an OMORI moveset that I've been trying to write for a while. Not sure if I did a good job at including elements from his game but I'm happy that I kept it (almost) entirely spoiler-free. Might make extra stuff like victory animations later if I feel like it.
Guh-Huzzah!
Metal Shop X
Neutral Attack: Slashes in front of him with his knife thrice
Dash Attack: Holds his knife with two hands and thrusts it forward (STAB)
Forward Tilt: Steps forward and slashes upwards, can be followed with a downward slash if the button is pressed again (ATTACK AGAIN)
Down Tilt: Sweeps his foot to trip the opponent (TRIP)
Up Tilt: Grips his knife backward and swings it above himself
Side Smash: Attacks forward with surprising ferocity, hitting three times and launching with the final hit (HACK AWAY). If he's HAPPY, he instead bounces a basketball on his knee before kicking it forward (CURVEBALL)
Down Smash: Cuts behind and in front of himself. If he's SAD, he instead swings a frying pan around himself near the ground (TENDERIZE)
Up Smash: Jumps twice, slashing upwards with each time. If he's ANGRY, he instead winds up and swings a baseball bat upwards (BEATDOWN)
Neutral Aerial: Somersaults and hits with his extended leg
Forward Aerial: A roundhouse kick followed by a knife hit
Back Aerial: Puts his knife under his arms and shoves it backward with his free hand
Up Aerial: Kicks upward
Down Aerial: Pulls a Sprout Mole out of nowhere and slams it downward
Grab: Uses Reaches out to grab the opponent with his free hand
Pummel: Headbutts them
Forward Throw: Shows the opponent forward with a shoulder check
Back Throw: Turns the opponent back and kicks them without looking at them
Down Throw: Trips the opponent down and stabs them multiple times
Up throw: Winds down and kicks the opponent upward with a stretch kick
Neutral Special: EMOTION CHART. Pulls out a book and reads it carefully. This special changes his emotion, respectively to SAD, HAPPY and ANGRY, with every input making him switch to the next emotion. A shield+special input resets his emotion to NEUTRAL. SAD makes him deal and take less damage/knockback; powering up his down special/smash. HAPPY makes him faster and lighter, powering up his side special/smash. ANGRY makes him hit harder and take more damage, powering up his up special/smash.
Side Special: MOCK. Sends a projectile in the form of multiple
signs. It travels horizontally and lowers the attack of any opponent it hits slightly. If he's HAPPY, this attack becomes HIT-AND-RUN, a kicked basketball that stays around longer and hits harder.
Up Special: LUCKY SLICE. Crouches before jumping upwards, slicing with his knife all the way up, and finishing with a final slash that has a low chance of dealing a critical hit. If he's ANGRY, this attack becomes TWIRL, traveling further and hitting with a spinning baseball bat attack at the end which deals more damage.
Down Special: BREAD SLICE. Readies his knife and thrusts it forward, dealing weak damage but immense knockback. If this attack hits an enemy, a Special Zoom will be triggered and a bread food item appears in front of him, healing 8%. If he's SAD, this attack becomes SNACK TIME, hitting with a frying pan instead of a knife. It deals more damage and creates a jam food item that heals 15%.
Final Smash: RELEASE ENERGY. A cinematic Final Smash that can be triggered by a group of spectral red hands that spring from the ground in front of him. Upon activation, it shows the player party joining him to beat down the enemy.