Hover over the icons under "Damage" to see list of attacks.
Dragon Lvl Weakness HP Damage 
Steampunk Dragon 38 
17,086 
6,097- Flying Kick: 5,448
- Flaming Arrows: 6,097
- Hard Charge: 5,503
- Magneto: 6,097
Dark Fire Dragon 39
19,599 7,471- Hard Charge: 6,292
- Leech: 6,886
- Nuclear Hit: 7,471
- Ghost Cloud: 7,471
Reward: 2 
and 30000 
Note: Remember to not use any physical attacks as they do little damage.
Strategy: Use Gummy Dragon for Dark Fire and Coral for Steampunk but you better choose a third dragon to insure your victory.
Your dragons at minimum should be level 15.