microcontrollers that can be programmed using ladder logic
A PLC is a microcontroller with firmware to run ladder logic. So, just about any microcontroller with sufficient resources would fill your need. All you need to add is the firmware for ladder logic.
There's a couple of open source projects that most likely fill your criteria that can run on a number of microcontrollers.
Here's one:
https://www.youtube.com/watch?v=Z6gFBM8AqIE