The series is propped up by Gyutaro, Doma, and Muzan's feats. Enmu's death is a distant 4th place. Hantengu's various forms have feats in the general ballpark of the train derailment and edging towards Gyutaro/Doma/Muzan's. Tengen's feat is difficult to gauge at best, and underwhelming at worst. Tanjirou splitting that boulder shouldn't be a highlight. Daki's feat should be more impressive than slicing the boulder, but the specifics of figuring out the surface area is too much of a pain in the ass for my liking because buildings are annoying like that. Both the Hand Demon Burrowing through the ground and the Spider Demon Swinging that tree should be comparable depending on how far and fast Tanjirou was sent flying. The strength of a Lower Moon's strongest and their overall durability is apparently several dozen times beyond Tanjirou's base strength in the Rui fight based on what he can cut with Water vs Sun Breathing. Rengoku derailing that train car is basically tacked on lacking for anything more notable.
Overall, somewhere in multi city block level once you hit the Hashira/Lower 1/Upper 6.
I'll upload speed feats to another set of posts when I can bother collecting them into imgur galleries