Answer:gainsay
Explanation: first of all contradict means Inconsistance
now let's look at the meanings for the other words
1.gainsay:to deny, dispute( engage in an argument; debate about something).
2.oppose:to disagree with something or someone.
3.disparage:To reduce in esteem or rank,Such as an demotion.
4.tarnish:To sully, soil, make dirty.