Is there a way I can have validation against the Relaxed group also execute the ungrouped constraints?

You can have Relaxed extend Default but that seems not what you want as per your other sentence.

So the constraint on a1 is the only thing not enforced when evaluating against the Relaxed group.

You could have another group, assign the constraint on a1 to that group and let Complete extend both, Relaxed and that other group.

I have to admit I'm a bit confused about your requirements after your last messages. Can you describe the constraints you have and which one you want to validate together and which ones not? And what the default behavior should be when no group is passed explicitly to validate()? What is the actual use case you want resolve (always helps to discuss an actual example)?