I just wanna throw out there watch out for your equipment durability one boss fight failure on this boss broke all 4 pieces of my aurous invisible set and my dark pyromancy flame, so just take that into account with this boss.

I just spammed lingering flame at him to win

You can bring Bashful Ray to this fight. When you start from Huntsman's Copse, first clear out all of the enemies up until the mist gate that leads to Executioner's Chariot. Now, do not enter the gate, but return back to the summoning place of Bashful Ray. Summon him and run to the mist gate, and he will follow. Once you step in, he'll come after you and help with the skeletons/necromancers and the boss. While he is not intelligent enough to run to alcoves to avoid the chariot, he does have a lot of hit points and can take a few chariot assaults.

For me, the best way to kill the boss was to equip a +10 dagger, run into the boss area, immediately throw an alluring skull to the right, then run on the left side and hide in the first corridor to avoid the horse. Then immediately run to the corridor the necromancer is in and spam it with R2 dagger attacks until it is dead. Stay in the corridor and wait for the horse to circle a few times to make sure all of the skeletons are dead. Then run back to the very beginning and hide in the corridor opposite to the fog door you entered. From that corridor, aim the bow in to your left and target where the boss will pass. A combination of lingering flame and great heavy soul arrows will reduce the health to the degree that it falls to the edge of the cliff. You then run down the hall and toss alluring skulls to keep the skeletons from bothering you. Once you get to the horse, one shot will cause it to fall off the cliff. You can then exit the boss room to avoid all of the skeletons chasing you.

The skeleton can use parry and stab back to you, I got hit and lost there.

Using a bow and arrows will easily defeat the crazy horse.

Another method: kill all necromancers as explained, and run to the pit the chariot jumps over. Pull out a large club, and do batting practice with the chariot. If you're hugging the wall right next to the pit (I do the right side) the chariot cannot hurt you until after it lands. This is the cheapest and easiest way of killing it.

This is the one. This one right here. anyone who eventually gives up on this game will have one. This is the boss that beat me. Congratulations Miazaki. You have beat me.

The strategy of hiding in the alcoves as the chariot passes is stupid. Tried that multiple times and kept getting ganked by the skeletons. Its super easy just to roll through the blades. The timing isn’t that hard. Unless using alluring skulls to draw the attention of the skeletons I would avoid hiding in the alcoves