Arcanine

Once a top-performing Fire Type, Arcanine has slipped into obscurity. It's badly outclassed as a Fire Type, and its time as a pseudo-Electric Type is over as well. It's still well loved by many, and is a serviceable defender in the withered defense meta and an okay budget/early-game attacker, but it really doesn't provide any great utility at this point, as even the easily obtained Flareon out-paces it.

Best PvE Offensive Moveset

• Fire Fang benefits from STAB and should be paired with Fire-type charge moves.
• Flamethrower outclasses Fire Blast, offering nearly the same DPS at half the energy cost.

• Thunder Fang should be paired with Wild Charge to allow Arcanine to act as a pseudo Electric attacker, but consider other Pokemon instead. 

• Snarl is superior to Bite due to its higher energy gains.

• Crunch, Bulldoze*, and Psychic Fangs have no purpose on an offensive Arcanine.

Best PvE Defensive Moveset

• Thunder Fang is arguably the best on defense due to its potential at hurting Water-type attackers.

• Snarl and Fire Fang are both great as well depending on the Charged Move of choice.

• Don't expect Bite to do much at all to attackers.

• Wild Charge is a powerful and nasty surprise to Water-type counters, but pairing it with Thunder Fang makes Arcanine very vulnerable to Ground Types.

• Crunch, Flamethrower, and Scorching Sands are all optimal depending on the Fast Move.

• Psychic Fangs comes out frequently, but is to weak to be worth using.

• Fire Blast is underwhelming in every aspect.

In most situations, Snarl is the superior fast move due to its neutral coverage and superior energy generation, though Fire Fang gets STAB and allows Arcanine to act as a Fire Type attacker to a greater degree. Thunder Fang can be used to surprise Water-type Pokemon, but this likely isn't enough for Arcanine to win due to its poor bulk. 

Flamethrower (90 Power/55 Energy) is a decent Fire-Type STAB move, while Wild Charge (90 Power/50 Energy) provides important coverage and is an objectively good move on its own. Bulldoze and Scorching Sands provide useful coverage, but giving up other charge move options may not necessarily be worth it. 

While the previous moveset focuses more on a generalist approach, this moveset has a greater focus on Arcanine's performance as a lead. Fire Fang has good power and okay energy gain, which allows it to combine with the lesser energy of Crunch (70 Power/45 Energy) in order to produce shield pressure. Wild Charge is preferred in the final slot due to its ability to punish counters, though Flamethrower is also an option if additional fire-type coverage would be beneficial for an expected matchup.