A series made by our very own Ryan Swag, the primary focus is breaking down the most realistic and useful IV builds for specific Pokemon for the Great League and/or Ultra League. Note that while some of these may end up out of date as the game changes and new Pokemon are added, but the IV spreads mentioned should remain relevant for many matchups.
Many of these guides also have companion videos, so please take a look at Ryan Swag's Youtube Channel for these, as well as additional useful Pokemon Go content.
Goodra PvP IV Deep-Dive
Clodsire PvP IV Deep-Dive
Giratina - Origin Forme PvP IV Deep-Dive
Cresselia PvP IV Deep-Dive
Annihilape PvP IV Deep-Dive
Decidueye PvP IV Deep-Dive
Giratina - Altered Forme PvP IV Deep-Dive
Quagsire PvP IV Deep-Dive
Wing Attack Charizard PvP IV Deep-Dive
Carbink PvP IV Deep-Dive
Greninja PvP IV Deep-Dive
Sneasler PvP IV Deep-Dive
Shadow Alolan Sandslash PvP IV Deep-Dive
Haxorus PvP IV Deep-Dive
Tapu Fini PvP IV Deep-Dive
Shadow Victreebel PvP IV Deep-Dive
Slowpoke Family PvP IV Deep-Dive
Chesnaught PvP IV Deep-Dive
Cobalion PvP IV Deep-Dive
Virizion PvP IV Deep-Dive
Guzzlord PvP IV Deep-Dive
Toxapex PvP IV Deep-Dive
Dubwool PvP IV Deep-Dive
Galarian Stunfisk PvP IV Deep-Dive
Malamar PvP IV Deep-Dive
Deoxys - Defense: PvP IV Deep Dive Analysis
Is Your Buzzwole Bad?
Scrafty PvP IV Deep-Dive
Obstagoon PvP IV Deep-Dive
Lickitung PvP IV Deep-Dive
Eeveelutions PvP IV Deep-Dive
Cofagrigus PvP IV Deep-Dive
Trevenant PvP IV Deep Dive
Sableye PvP IV Deep Dive
Noctowl PVP IV Deep Dive
Walrein PvP IV Deep Dive
Venusaur PvP IV Deep Dive
Shadow Nidoqueen PvP IV Deep Dive
Diggersby PvP IV Deep-Dive