Rapidash

Rapidash looks cool, but its performance sure isn’t. Though it has access to Fire Spin, it doesn’t learn Overheat, making it totally meta-irrelevant. It’s just another Fire-type in a crowd of better Fire-types.

Best PvE Offensive Moveset

• Fire Spin performs the best in PvE offense, and is superior to other options.
• Incinerate is a direct downgrade in PvE.
• Ember is an even further downgrade.
• Low Kick lacks STAB and has no use. 
• Fire Blast is the best charge move available for offense. 
• Heat Wave is a downgrade and performs less optimally. 
• Flame Charge has poor damage output despite being a 3-bar move.
• Scorching Sands, Wild Charge*, and Drill Run are actually quite good in PvE, but lack STAB with Rapidash. 

Best PvE Defensive Moveset

• Incinerate is the best fast move on defense due to its tremendous base power.
• Fire Spin is the next best available, but the difference is significant. 
• Ember has less damage output, and shouldn't be used.
• Low Kick may offer a different type coverage, but lacks STAB and has the worst damage output. 
• Scorching Sands is arguably the best for defense thanks to its coverage, respectable damage, and being a 2-bar move.
• Wild Charge* is also outstanding on defense, and sports counter-coverage against Water Types.
• Drill Run is basically a worse Scorching Sands on defense.
• Flame Charge can be access more frequently as a 3-bar move, but is quite easy to dodge.
• Fire Blast hits hard, but Rapidash may feint before being able to use it. 
• Heat Wave is slow to access and easy to dodge, making it the worst option on defense. 

Incinerate features superior damage output and energy generation on paper, but in practice its long animation can make it difficult to use. Fire Spin falls behind in energy gains; Ember is an even further downgrade. Low Kick sports the worst performance in both damage output and energy gains, and also lacks STAB. 

Drill Run is recommended for its wide coverage, efficient DPE (Damage Per Energy), and costs the least amount of energy among Rapidash's charge moves. Scorching Sands falls behind Drill Run with lower DPE and higher energy cost, though a gamble for an Attack drop might make it a decent gimmick with a bit of luck. Flame Charge demands less energy than other charge move options, and while it's not as powerful, it still provides a guaranteed +1 ATK self buff. Wild Charge* sports high raw power and counter-coverage against Would-be Water Type counters, making it very much worth considering. Fire Blast and Heat Wave both cost too much energy to be worthwhile.