What is the best 2nd level spell to concentrate on to maximize damage?

In a party full of crowd control, the Magus wishes to dish out as much damage as possible. What concentration spell will allow them to do that, under the given circumstance:

  • The Magus is 4th level, any race, any class/multiclass, feats available
  • The damage is dealt out over 1 minute maximum
  • The rest of the party is focused on their own goals, so any preparation or buffs on the Magus will have to come from themselves: (no time limit)
  • Assume things go perfectly 100% of the time: ie enemies will always fail on saving throws, the Magus will always succeed on an attack roll, disregard advantage and disadvantage
  • The only source of damage tracked comes from the Magus’ concentration spell; no need to worry about ensuring their action is free every round to cast another damaging spell
  • Assume all damage is average: 1d6 = 3.5 damage, don’t round
  • If a spell can hit multiple targets, there are 2 available each round
  • These 2 enemies behave optimally for your damage: if an enemy must end its turn in the spells area to take its damage, then 2 enemies in a round will do so.