間違えたのは君じゃないか！

to make a mistake (in); to commit an error (e.g. in calculation); to confuse; to mistake something for something else

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

you; buddy; pal; monarch; ruler; sovereign; (one's) master

then; well; so; well then; combination of 'de' and 'wa' particles; plain copula

indicates a question (sometimes rhetorical); or; whether or not; some- (e.g. something, someone); indicates doubt, uncertainty, etc.; emphatic prefix; suffix forming adjectives or adverbs; in that way