Pedals take a lot of abuse (weather and crud from the road) and are designed to last for many miles. They are rarely removed before they wear out unless removing for transportation. When it comes to removal many get confused as the left pedal has a “left handed” thread i.e. it tightens anti-clockwise.
Alway use plenty of grease when fitting pedals.
Don’t leave it until the last moment if you need to remove pedals e.g. fitting in a bike box. You may require a lot of force and a large spanner/hex wrench. The weeny multi-tool may not be be up to it.
Don’t forget to pack the tool in the bike box to re-fit the pedals!
Shimano pedals typically use a a 15mm spanner or/and 6 or 8mm hex. Look pedals use 8mm hex.
The image and download below should help.