Which Scared Seal is the best out of all of them?
A scared seal? That sounds depressing, I like seals. They’re awesome creatures in ocean life.
I’m going to assume you meant Sacred Seal. There is no “best Sacred Seal”, but there are ones you should prioritize on upgrading. Anything with a 240 SP weight (QR, HB, CD/DD, ploys, atk smoke, drive def, etc.) should be highest priority for competitive utilization.
Embla's ward, of course
Other than that, Quick Riposte is generally pretty good, heavy blade on some builds, distant def is always a good option, quickened pulse, panic ploy. These are probably the best for a single build, or for specific characters.
If you mean best overall for all characters to use, I think every character would appreciate atk +3 and the squad seal atk +3
Pokemon GO
Fire Emblem Heroes
Fate Grand Order
Dragonball Legends
Dragalia Lost
IV Calc
Heroes