Gwyn, Lord of Cinder

You are now near the end of your SL1 journey. One more boss remains to be defeated. Before fighting the final boss, do whatever you need to do and complete whatever quest line you need to complete. In particular, stock up on consumables and upgrade materials. Upgrades and/or ascend weapons you want to experiment in NG+1.

Kiln of the First Flame

If you have not already done so, sit at the bonfire before the kiln and offer the Lord Souls to open the gate to the kiln. Farm the Black Knights within to stock up on Titanite Chunks and Blue/Red/White Titanite Chunks.

Gwyn, Lord of Cinder

96. SL1 Gwyn, Lord of Cinder, Dark Souls: Remastered

Equip the Chaos Reinforced Club+4 (a +5 is better if you have it) and have at least 10 soft Humanities. Equip the Grass Crest Shield and the Mask of the Child. Trigger the effect of the Red Tearstone Ring. The most effective strategy against Gwyn is to parry his horizontal swing attacks. Enter the fog wall and move in some distance toward Gwyn. Wait for him to perform a flying dash at you and slash his sword. Parry the attack and riposte. Strafe behind Gwyn and R1. Roll through his attacks as necessary. You can manipulate Gwyn into performing the horizontal swing attack so you can parry and riposte. After strafing behind Gwyn, drink from your Estus Flask and Gwyn would perform a horizontal swing of his sword. Parry the attack and riposte. Rinse and repeat.