The Destroyer:

• Bring something like a pumpkin pie, marshmallow on a stick, or a bowl of soup.
• Star Veil, or a cross necklace would be VERY helpful, it will hit maybe two or 3 segments whenever you get hurt
• The magma stone, or the full set of frost armor would inflict extra damage to the destroyer so i would recommend it.
• Fishron, frozen, or leaf wings are required, because he will come up from underneath you.
• Horseman's blade is very helpful, (as it spawns a pumpkin head comes and fights for you, the Terra blade is also very good choice.
• A chain gun, or galligator with exploding or clorophyte bullets will also be effective.
• If you get ahold of the queen spider staff, it would be very helpful in this fight, plus if you have a nimbus rod, you can put it on the destroyer, and makes maximum damage, and kills the probes.
• The star cannon is very useful because of its high damage and piercing ability.