The Legendary Swordmaster: Only I Have the Power to Forge Swords from Monsters is a Manga/Manhwa/Manhua in english language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.nl fastest updating comic site. The Summary is

What kind of magic sword will you become…?” The protagonist, Touji Nanase, who was constantly harassed by debt collectors and bullied by his boss at a toxic job, gets sucked into a dungeon that suddenly appears and is attacked by monsters! As he teeters on the brink of death, he gains a legendary item and awakens a cheat skill called “Magic Swordsman,” allowing him to transform defeated monsters into swords. Though people mistake him for a monster due to his sinister appearance and ruthless nature, he sets out on a path of revenge against those who made his life miserable…! A classic dark fantasy of revenge and overwhelming power!