Nell is the best luck CO (better than Jugger or Flak). Luck is added to firepower. So a 10 HP infantry has
1 - 1 +luck% damage range versus a Mega tank with no defence bonuses. (the 1 comes from the fact that an infantry has a base damage of 1% against mega tanks, see damage Chart). in this equation luck is a random number between 1 and 10 for most COs, however for Nell it is a random number between 1 and 20. This significantly improves the chance an infantry can damage a Mega tank.
Lucky (0-20% more damage)
Her day-to-day makes all units something stronger, especially when you do little damage to your opponents (see summary). Especially when you use your SCOP or COP. Her SCOP allows even her infantry to severely damage any unit it can attack. For example if you use your SCOP and attack an Mega tank (without defence boost) with a 10 HP it will do a random damage between 1-101%. This example shows that even weak units can severely damage your opponents units if Nell uses her SCOP. The more units you have, the more usefull her SCOP power will be.
-Luck is still luck, so you may do lots of damage to an opponent. However you may also do normal damage to opponents. So this will not always help you to break through stalemates.
- luck is also affected by the unit HP and the defense boost of an opponent (a 5HP unit has only half the luck range compared to a 10 HP unit, If your opponent has +30 defense it will also affect the extra damage which is provided by luck)
- during her SCOP an infantry unit with 10 HP has a 7.7-107.7% damage range against Battlecopters and a 1-101% damage range against megatanks. I mention this to show that luck is not affected by the amount of damage an infantry does without luck. So if Nell uses her SCOP, take your chances and attack strong opponent units with disposable units.