How did asoka apparently feel after conquering kalinga? why did he feel that way?

I answered a question similar to this a little while ago.  I'll repeat some of that comment here, and refer you to that other answer as well.

Asoka was ruler from 268 to 232 BC of lands that would later become known as India.  Asoka was a great conqueror but also someone who found enlightenment through Buddhism.  After conquering the Kalinga region in eastern India, rather than feeling some great rush of pride or accomplishment because of their victory, Asoka felt guilty.  So he worked hard to improve the lives of the Kalinga people that he had conquered.  Conquest was not something to be celebrated triumphantly.  Rather, conquerors had an obligation to those whom they had conquered.
Read more on - link

C.before he invaded rome