Shadow Magmortar

Shadow Magmortar is best described as "usable". It's not exceptional by any means, but it can get the job done when a Fire Type is needed. Just don't invest too heavily into it....

Best PvE Offensive Moveset

• Fire Spin is the move with STAB and suitable for Shadow Magmortar as a Fire specialist.
• Fire Punch and Fire Blast are very close, with the former being more dodge friendly.
• Brick Break and Psychic are just not appropriate on Shadow Magmortar. TM those.
• Thunderbolt* and Scorching Sands lack STAB and don't have any use on offense. 

Best PvE Defensive Moveset

• Fire Spin is much more damaging than Karate Chop on defense.
• Brick Break is hard to dodge and is not resisted by Shadow Magmortar’s common counters.
• Fire Punch is stronger than Brick Break and also has 3 bars.
• Psychic and Scorching Sands have relevant defensive coverage and 2 bars.
• Fire Blast is not likely to get used at all before Shadow Magmortar faints. 
• Thunderbolt* might be useful to hurt Water-type attackers, but that's about it.