Just like group prayer, group karma is absurd act. Personal intent of each individual is important while performing in group. It helps all but individually, same as group karma of a battle between Kaurav and Pandava and for example Bhishma, the innocent one, took side of Kaurav and suffered till death but died at will ie death of a sage and became free from cycle of birth and death. His intent was his surrender to the King, that remained pure till end. But in contrast to it if a person is attending pooja with intent to snatch jewellery from neck of women then he will have to reap his sown intent individually.

Karma is totally individual, because journey of Dharma or seeking the self or realising the consciousness or seeing the truth is personal responsibility and personal journey.

Britishers occupied India but benefitted it 200 times by Railway line, Education, Industry, Postal and Military services, Prepared Map of whole India united it as one nation. Democracy and removal of cast discrimination, and rise of recognition on merit basis, Women education etc etc long list it is. Whole there were people bringing to our religion who tortured poor and uneducated in the name of English rule. Today both are reaping their intent or not?