With a powerful weapon, those at the tenth transformation of the first mortal coil can double their power, which will put their power at 20 units. That is the minimum power of those at the second mortal coil.
Those who are at the second mortal coil can burst out with a power that is more than what their body can produce on its own. It is because of something called force.
With 100% control of the power of the body, one can begin to manipulate internal and external force to amplify their power. This power can be twice as much power as they can produce on their own or eleven times. So the power of those at the second mortal coil ranges from 20 to 110 units.
The best way for others to narrow the gap between the first mortal coil and the second mortal coil is a powerful weapon or defensive artifact.