Aww yeah, I've had a lot of fun with Typhlosion in doubles. It needs a bit of setup and support to shine but it can be devastating if used right. Flash Fire, Eruption, decent stats, decent coverage, it has enough to work with.
Typhlosion @ Firium Z
Ability: Flash Fire
EVs: 252 Sp.Atk, 252 Speed, 4 HP
Modest nature
-Eruption
-Flamethrower
-Protect
-Focus Blast
This is the set I've been using in doubles. I use a Weakness Policy Musharna with Baton Pass to get in safely while a Torkoal uses Lava Plume. It simultaneously gets Typhlosion in safely and activates Flash Fire because Torkoal is pretty much the only thing slower than Musharna. A lot of opponents go for super effective damage on Musharna, anticipating a Trick Room setup, which activates Weakness Policy, and Musharna is bulky enough to survive most super effective hits with ease (to give an idea, Mega Alakazam usually fails to even hit 50% damage with Shadow Ball). This way, after a single turn of setup, I've got a +2 Sp.Atk Typhlosion on the field at full health, with sunlight, and Flash Fire activated, which is enough power to OHKO even the most defensive Cresselia with Eruption, and simultaneously it's not uncommon for Lava Plume to burn at least one opponent. It also has enough power to KO defensive Tapu Fini after Lava Plume damage with Eruption. Most teams can't handle that kind of power and crumble. On the second turn I usually switch Torkoal out and switch in Lilligant, which provides speed support with Chlorophyll After You to outspeed most opponents. Firium Z gives Typhlosion a devastating fire attack to use if it gets damaged, needs to go through particularly sturdy opposition, or anticipates a Protect. For instance:
+2 252+ Sp.Atk Flash Fire Typhlosion Inferno Overdrive (200 BP) vs. 0 HP / 4 Sp.Def Multiscale Dragonite in sun: 185-218 (111.4 - 131.3%) -- guaranteed OHKO
+2 252+ Sp.Atk Flash Fire Typhlosion Eruption (150 BP) vs. 252 HP / 44+ Sp.Def Tapu Fini in sun with doubles spread damage: 147-173 (83 - 97.7%) -- guaranteed KO after Torkoal's Lava Plume damage
+2 252+ Sp.Atk Flash Fire Typhlosion Eruption (150 BP) vs. 252 HP / 252+ Sp.Def Cresselia in sun with doubles spread damage: 253-298 (111.4 - 131.2%) -- guaranteed OHKO
+2 252+ Sp.Atk Flash Fire Typhlosion Eruption (150 BP) vs. 4 HP / 0 Sp.Def Mega Salamence in sun with doubles spread damage: 229-270 (133.9 - 157.8%) -- guaranteed OHKO
+2 252+ Sp.Atk Flash Fire Typhlosion Eruption (150 BP) vs. 0 HP / 4 Sp.Def Mega Latias in sun with doubles spread damage: 147-173 (94.8 - 111.6%) -- guaranteed KO after Torkoal's Lava Plume damage
Typhlosion is the only pokémon that can get this kind of power because of the combination of Flash Fire and Eruption. Heatran gets that too but Eruption Heatran is banned on the battle spot and is very difficult to find legit nowadays. If I get the Weakness Policy setup off it just destroys even pokémon that resist fire in a single hit like Mega Salamence and Incineroar. Even Mega Latias crumbles, and Mega Latias has a base 150 Sp.Def stat. With After You support from Lilligant it's absolutely devastating and almost impossible to revenge kill and I win most battles with it. Recognise that the Z-Move OHKOs Dragonite, which has effectively a 4x resistance thanks to Multiscale, and realise that a lot of pokémon around those defensive ranges get OHKOd through Protect on neutral hits with it. I've had so much fun with it. It doesn't win every battle of course, there are ways of stopping it and you shouldn't go into the free battle spot where Primal Kyogre just wrecks you, but it's pretty solid and not a lot of people run Typhlosion. It is somewhat gimmicky, it's far from the meta, but the power you get after a single turn of setup is terrifying.