This is a showcase about Morpeko’s strength in exploiting and defeating ANY Team Rocket Grunt, leader, or Giovanni! Here’s what you need to do to pull this off with your own morpeko! No PvP IVs required!
Basically, all you need is a Morpeko with the following: Thunder shock as the fast move, and 2 charged attacks, one of which is psychic fangs (I prefer aura wheel as the other). power it up if you want to speed things up (or use in GBL). This is the most expensive part of the step, but it is highly recommended (potentially outright required, but should still be viable with Psychic fangs only. Just slow.)
Method: Slot Morpeko 2nd or 3rd in your party, and immediately switch it in to delay the rocket member. thunder shock charges the gauge fast enough you should only eat 0-2 fast attacks before you get psychic fangs off, and then because of the delay grunts/leaders have after using a charge move + the form change, Morpeko can get another charged move off. turns into an infinite combo if executed right.
For Giovanni & the leaders, best to use Psy fangs twice for the defense drop (which applies even thru their shield)