What other Pokémon that can be OHKOed /2HKOed with 24 Atk EVs, that 0 Atk EVs normally can't with Pursuit?
Generally, to squeeze the most out of EVs, it's best to use the boosting nature on the highest base stat (for 252/252 spreads that just aim to maximise two stats this isn't an issue). Since you wanted to run Pursuit, and Latios is the most common Defog user in OU, having a guaranteed OHKO on it if it tried to switch out would be useful (with 24 attack EVs you also get 24+ Atk Tyranitar Pursuit vs. 0 HP / 0 Def Latias: 138-164 (45.8 - 54.4%), so if Latias switches out and you get Stealth Rocks up, it can't come back in ). You need 339 attack (148 attack evs, or 20 with a positive nature+) to guarantee doing over 50% to 0 HP / 0 Def Latios, but for a base stat ending in 4, like Tyranitar's 134 attack, there's an EV jump point at 24 [20+ attack Tyranitar = 339, 24+ attack Tyranitar = 341], so I decided to bump the attack up slightly higher to reach this and make the most efficient use out of Tyranitar's EVs.
Let's say I'm using 248 HP, 24+ Atk, 224 Def, 12 SpD, then I get 403 HP, 341 Atk, 312 Def, 239 SpD
but if I ran a defense boosting nature and aimed for the same 339 attack, I'd need 248 HP, 140 Atk, 12 SpD, with 108+ Def left over, which would give me totals of 403 HP, 339 Atk, 311 Def and 12 SpD, which leaves Tyranitar with slightly lower attack and defense. As a positive nature gives a 10% boost to the stats, when you're investing in multiple stats, where possible, it's more beneficial to place it in the highest stat.