How to crush PETROFF defence?

The Petroff leads to symmetrical pawn structures, in general, which makes it harder to create and take advantage of mistakes.  The most interesting games, in my experience, come where you vary the pawn structure or just avoid it altogethe

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Great...

Check out my another question ( how to crush the KING'S INDIAN DEFENCE)

@AviaSharma You can't "crush" any opening just like that! Petroff and KID are highly respected openings. 

You already answered your own question to some extent. If you play 3. Nc3 then you are already out of Petrov's Defense and into the Petrov Three Knights Game. Most commonly Black responds with 3. Nc6, then you are into yet another opening, the Four Knights Game.

1. e4 e5 2. Nf3 Nf6 {Petrov's Defense.} 3. Nc3 {Petrov Three Knights Game.} Nc6 {Four Knights Game.}

The Four Knights Game is also drawish, like Petrov's Defense, but probably you don't need to memorize as much as in Petrov's Defense. From there, the most ambitious move for White is 4. Bb5, which is the Spanish Variation of the Four Knights Game, ambitious because it is roughly a transposition of the ambitious Ruy Lopez, but a quieter continuation that is also strong is 4. Bc4, the Giuoco Piano, and note that "piano" is Italian for "quiet" or "soft," so again the opening will tend to be drawish. As others noted above, these are all sound, very old openings, so you're not going to "crush" them by playing some secret, magical move.

P.S.--I made a slight correction above: Petrov Three Knights Game is slightly different than the usual Three Knights Game.

The best way to find a good line against the Petrov as white is to play it as Black for a while. Nxf7 after Nxe5 is probably the most feared line for Black but it all depends on your opponent. A good player will know ALL the sacking lines.