I will answer this with ‘intellectual curiosity’.
But, if you want some metrics: should be ELC, should have 10+ weighted classes, should have 25+ A-G classes.
ECs/Activities: Something interesting. I know this is vague. But, do something you love instead of checking boxes.
I’ll give you an example: swimmer with many local awards, volunteers with local charities helping kids learn how to swim, surfing passion, bodysurfing awards, lifeguard, EMT certified.
For the UCs, your PIQs should show who you are, not highlight your achievements. Can you imagine how many applications they read that are exactly the same? Show your voice.