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My opinion is completely different from yours.
Literal
I [of-の] opinion [topic-は] your opinion [with-と] completely differs.
The pattern [X]は[Y]と全く違う ('X is completely different from Y') uses と for the standard of comparison and 全く ('completely') as a strong intensifier. Repeating 意見 explicitly on both sides — rather than eliding the second one with 君の — gives the contrast extra weight, making the disagreement feel more pointed.