Q: If a child makes a mistake out of ignorance or delusion, that he is not aware of as wrong in the first place, the child will suffer from negative karma to a lesser degree, right?
A: Whether driven by ignorance/delusion or not, the intensity of (un)wholesome karma created is determined by the intensity of (un)wholesome intention (or motivation) involved. Usually, children are not motivated by intense evil (greed, hatred, delusion). Thus, there is less negative karma created.
Q: Recently, a mentally ill person was caught burning two men with kerosene. I think this person will suffer from negative karma to a lesser degree, right?
A: It is hard to judge how mentally ill he was if we are not good doctors. However, the process he went through to hurt the men was more complex than what even the severely mentally ill would usually do. There has to intentions to get the fuel, to locate the men, to pour the fuel and to ignite it. It’s rather hard to go through this elaborate process without clear intentions that he kept track of deliberately, perhaps with the clear aim to cause harm, as driven by hate? Then again, we can’t read his mind to judge this case accurately.