Outranging your opponent is always an option to be considered. If you have a squid or goldfish, consider taking the fieldgun or artemis as a side gun for this purpose. If you can force close combat fights, you can use carronade + flamethrower combination to destroy weapons, balloon and then everything else. When using ships like the spire you can either go for fieldgun + flak combo or attempt to disable and outdps him with double chaingun + hwacha. Mobula and Galleon can also outdps a Pyramidion at whatever range they decide to pick a fight.
Squid players should keep in mind that the pyramidion players easily get confused on the hull armor's status. Because it goes down so quickly, it is repaired as quickly. If they are emptying their flak/mortar while you bring up the hull again, they lose out on the majority of their damage. Use this to your advantage and either flee the scene or get in pyramidion's dead angle. As a junker, just try to get the 3 guns on him, you will outdps the pyramidion by a decent margin.
There are basic ways to stop basic pyramidion players. Players can adjust to these strategies and then it is up for you to adjust to that. As you get more and more experience you will learn how to deal with the ship better and better. Just think about what the ship's intentions are, what its range is and what the ship is doing. Every choice any player makes on his ship reveals a strength and a weakness. If a player tells his crew to man the front guns, he's weaker at the sides, if he tells the players to man the left side guns, he's weaker at the front but stronger at the side. By making his crew run, you can also avoid getting fired at.