Unnerve or Intimidate I guess?

When it enters battle it causes an earthquake because of it's weight

It is immune to everything

Truant

Because

Either Infriltrator (Spiritomb's Ability) or Wonder Guard (Shedinja's Ability)

It has 1 hp

It has sturdy

Every time sturdy activates

It gets +10% atk

And can stack up to 50 times

(shedinja but insane)

Ability that makes every move ohko and bypass abilities and sub and protect

Give it cursed body