Discourager

Dis·cour'a·ger noun One who discourages. « The promoter of truth and the discourager of error.» Sir G. C. Lewis.
Found on http://www.encyclo.co.uk/webster/D/79

Discourager

• (n.) One who discourages.
Found on http://thinkexist.com/dictionary/meaning/discourager/
No exact match found