can we reassume the advantages and win conditions for each other?
so Pupitar can use a lot of attacks, tough most of them Tatsumi can resist to them with RE and his RPL get him stronger and faster
"It would be a No Limits Fallacy to assume someone with this power can obtain any ability whatsoever. Its extent and complexity only go as far its feats and scaling have gone for it, in relation up to countermeasures to powers that already exist in the setting or similar, in a case by case basis."
I'm partially skeptical that it could give him Resistance to stuff like Earth Manipulation, Draconic Energy Manipulation (Especially when Incursio is made from a dragon's body itself.), Darkness Manipulation, given it's only given him resistance to extreme temperatures, electricity, poison, & time stop, AFAIK.
& even then it can still blast him with Energy Manipulation via Hyper Beam.
He needs to develop a lot of Resistances to resist all of Pupitar's attacks, but it sounds like he only gains resistances 1 at a time, after being hit.
if Pupitar use outrage Tatsumi is smart and skilled enough to dodge and become invisible and waiting till Pupitar become confused and hit him
If he dodges, it can use Stomping Tantrum to hit him with an AoE that's at double strength because Pupitar's previous attack missed.
the real problem are the amps of Pupitar, but thanks to Tatsumi own supernatural willpower, awakened power, and Incursio RE can eventually deal with them
Does Tatsumi have Resistance to Fear Manipulation? If not, Pupitar can drop his Speed with Scary Face, & even once is likely good enough to get some hits in.
Or boost its own & its AP with Dragon Dance.
Or just Sandstorm to obscure Tatsumi's visibility, & then use other attacks, like Stone Edge to make rocks below where Tatsumi stands or Stealth Rock for a homing attack.
& there's the IQ Skills it has, for being in Group C.
I'll omit ones that seem irrelevant:
Course Checker Refrains from attacks that would be blocked by walls or allies.
Item Catcher Can catch a Throwing Item and keep it for its own.
Brick-Tough Adds 10 to max HP. Cannot be turned off.
(Presumably, Brick-Tough is analogous to having a small amount of extra Stamina.)
Concentrator Raises Accuracy by 1 but decreases Evasion by 1.
(May help against Tatsumi trying to dodge.)
Practice Swinger Raises Attack and Special Attack by 1 on the turn after a missed attack.
(Any time Tatsumi dodges, Pupitar's next attack will hit harder, & it has several AoE moves.)
Aggressor Raises both Attack stats by 1 each, but decreases both Defense stats by 1 each.
(More offenses. In theory, Pupitar could compensate for this with Iron Defense, but it's skeptical it'd do this.)
Counter Basher Lowers Defense by 1, and sometimes sends the damage taken back to the foe if the foe is adjacent.
(In gameplay, this is a 12% chance to counterattack adjacent foe for 100% of damage taken. Which'd likely hurt Tatsumi a lot.)
Clutch Performer Raises Evasion by 2 when HP is below 25%.
Extra Striker Sometimes strikes again following an attack.
Intimidator Sometimes causes attacking foe to cringe.
(As mentioned earlier, Cringing is the Mystery Dungeon Game's version of the Flinch status, where, in gameplay, the victim takes no action during the turn they were afflicted with the status. Could definitely create an opening against Tatsumi. Bulbapedia says in detail about it:
"33% chance to cancel an incoming close-ranged attack, regardless of the direction the attacker is facing. PP is still deducted from the attacker. Attackers with Inner Focus are unaffected. Does not affect line-of-sight moves, room-range moves, or thrown items. Can affect allies if they target the Intimidator with a close-ranged move for any reason.")