This is about a guy who has the highest kill rate in a game. At the beginning of the manga he was hired to take out a guild and used mechanical birds and such to attack then planted bombs at the bottom of the guild building. Afterwards he receives a commission from a Goddess and was sent to another world to assassinate someone I don't remember who. He was isekai'd and had his skills but all his items were no longer there so he created a hut in the middle of the forest and started foraging for supplies and killed a poisonous frog or toad and extracted the poison. Later he saved a King and princess along with the guard knight.

Ansatsu Skill de Isekai Saikyou - Renkinjutsu to Ansatsujutsu o Kiwameta Ore wa, Sekai o Kage kara Shihai Suru

~4400 manga completed
~1700 ongoing...

Yay, thank you, you're the best!!!!