With a medium stack in a tournament, handling aggressive opponents requires a careful balance of patience and strategic timing. Since your stack isn’t large enough to pressure them consistently, it's essential to choose spots wisely rather than engage frequently. Start by observing their patterns to identify when they tend to raise aggressively or bluff. You can then capitalize on these tendencies with strong hands or by reraising (3-betting) selectively, making them think twice about challenging you without a premium hand.