Best to-do list software for both iOS and Windows?

[Darth-Veger]

So basically i am looking for some software where i can put in what i like to be done on a day and that i can check and edit the to-do's on both Windows (or web browser) and my iPhone (iOS)
I tried looking and tried 2 but both either hit you with a monthly subscription model or are far too complicated as i just want to have the to-do list with perhaps some additional features.

[lordcrypto]

wunderlist (definitely a simple todo list)
trello (a bit more complex with a board system, but can be used as a todo list)