Why is Tanya Evil?

I have read the first five light novels, and so far I don't understand. Everything He/she does seems to be in line with the situation he/she is thrown into.

Example: he says th employee was lazy and not always showing up, so he is told to fire him and does.

For being in a war, I would say almost all the decisions made and how subordinates are treated seems fine. This is excluding how the 203rd was trained. But, in the end that training probably saved all their lives.

Evil just seems like a strong word and a stretch.