To give more details on Pachirisu and this Pachirisu in particular:
Pachirisuâs stats arenât great. They arenât terrible, but they arenât great. Of the four Pokemon involved in this particular exchange, Salamence and Garchomp have a base stat total of 600, Mega Tyranitar has 700, and Pachirisu has 405. Yeah.
To make things worse, Pachirisu is a gimmick Pokemon of a class known as a âPikachu cloneâ. Its entire purpose is to be a generic Electric-type with middling stats and chubby cheeks. It was never built for high-level play, and a lot of people will even say that itâs not worth it for casual because there are so many better Electric-types.
Pachirisu does have a couple of things going for it, though. Firstly, its Special Defence and Speed stats arenât totally garbage, and its Defence isnât bad either. This means that it can take a hit if you train it right (which Se Jun did).
Secondly, the moveset that this particular Pachirisu had was a brilliant one for what Se Jun wanted it to do. Nuzzle deals a tiny amount of damage but is guaranteed to paralyse anything that isnât an Electric- or Ground-type. Paralysis halves speed and gives you a 50/50 chance of not being able to do anything that turn. Thatâs HUGE. This is a game in which most major attackers are fast as hell, and outspeeding is vital to pretty much all strategies.
Super Fang, as mentioned, is guaranteed to do 50% damage to anything thatâs not a Ghost-type. Pachirisu cannot explicitly KO with this, but what it can do is break down its opponentsâ defences. You canât use inventory items in competitive play, so itâs unlikely that this damage will be healed, and 50% damage can make the difference between Pachirisuâs partner taking two moves to defeat its opponent vs taking one move.
Follow Me redirects opponentsâ moves onto Pachirisu if they would have otherwise hit Pachirisuâs partner. This lead to the instance above, in which Pachirisu survived a hit from a Draco Meteor (a 130 power attack in a game where 90 power is considered excellent and 100 power or above generally requires major drawbacks). You might think âbut if it couldnât take out Pachirisu, then it couldnât take out the Salamence it was meant for, right?â NOPE: Salamence is weak to Dragon-type attacks like Draco Meteor and so would have taken double damage. Thatâs probably a KO.
But the real purpose of Follow Me was for Pachirisuâs intended partner: Gyarados. Depending on the situation, Gyarados takes either double or quadruple damage from Electric-type attacks, which is a shame because Gyarados is otherwise terrifying. Pachirisu has the passive ability Volt Absorb, which means that itâs healed by Electric-type attacks rather than taking damage from them. So if you try to use an Electric-type attack on that Gyarados thereâs a very good chance that you will end up healing Pachirisu instead. Not what you want, especially when this particular Pachirisu is so unbelievably bulky.
Oh, and its last move is Protect, which totally nullifies damage on Pachirisu for that turn. Useful if Pachirisu canât do anything useful this turn but you donât want to swap it out.
And that Sitrus Berry? Yeah, that thing recovers 25% of Pachirisuâs total HP the moment it goes below 30% total. So if you just barely fail to kill Pachirisu, itâs going to heal itself. Have fun.
The last thing Pachirisu has going for it, at least in this case, is intimidation. The universal response to this team was âWho the fuck brings a fucking Pachirisu to the World Championship?!â But then you realise that Se Jun is totally serious about this ridiculous plan. And then you realise that itâs working. And then you realise: oh shit, this guy is really good. He knows what heâs doing with this.
TL;DR: By all accounts Pachirisu should have been an utterly stupid thing to bring to this level of play, but in practise it was a very clever set-up that took advantage of its decent defensive stats and useful support/survival movepool.