Age of Empires II: Definitive Edition

Set up a Standard Game with the following settings:

• Game Mode: Regicide
• Click Yes to Regicide Rules
• Resources: Infinite
• Population: 500
• Starting Age: Castle Age
• Difficulty: Standard

Start the Game

1. Using Villagers build 3 - 4 castles
2. Build houses until the pop. limit is around 100 (Double press Q with a villager for fast select)
3. Select Castle, hold shift & Click Recruit Petard 3 times - Do this until you have 60+
4. Select castle and press the eye icon (Reveals enemy king location)
5. Send all petards to attack the building the king is garrisoned in.
6. The king will attempt to escape before the building is destroyed, select your petards to attack the king when he flees
7. Once killed, the achievement will pop

You will also unlock the following:

The The King Is Dead, Long Live the King! achievement in Age of Empires II: Definitive Edition worth 19 pointsWin a Regicide game.

Start a new Regicide game any difficulty, any enemy.
Pick any civilization except the Koreans, who can't build the demo ship (although they can build the petard if you're okay taking a bit longer). Select the "Real World - Earth" map type. I think it's a little easier to see what's going on with the Full Visibility option. Pick infinite resources, and starting age post-imperial.

You start in Antarctica with three villagers, a transport ship, and your scout. Your opponent has the same... and will immediately move everything but the king into their transport and sail to South Africa. Move two villagers to South America or Australia, and have your third begin to build a dock, and queue up a demolition ship. As soon as the two villagers reach land, have them build two houses. Once the demo ship is done, it should be able to immediately kill the king, it can sail further into the ice then you'd expect. Worst case scenario, if the king moves too far out of the way, move south of him and whack him once or twice with your scout to force him to move north.

If the king refuses to move toward the water and has too low HP for your scout to hit him again, you can always build a castle in South America/Australia and ship some petards back. It'd still be easier than a standard solution, since the enemy won't bother defending him at all. I've tested this a few times and have never needed to do that, though.