Hades didn't have cross save available at launch, which at that time mostly meant that Early Access players had to start from the beginning on Switch. Now the cross saves are here, and you can move PC saves to Switch and vice versa. This update also brings a number of post-launch patches from the PC version over to Switch.
Please be sure that your progress is in different save slots between PC and Switch! Instructions on how to move your PC saves to a different slot are in the Help & Info section on Switch (you just rename the save file).December 16, 2020
If you've already played the game prior to transferring, Supergiant reminds you to use different save slots for both platforms in order for things to work properly. If on the other hand you start a completely new game on either platform using a cross save, you'll immediately get all unlocks and relevant achievements you've already earned. You can find a description of how to transfer your data in the cross saves menu on Hades' title screen. Happy escaping!