Going from Korean to Cantonese (粵語) has a composite linguistic distance of 77% (curated lexical data). Below is the dimension-by-dimension breakdown.
Shared vocabulary, cognates, and loanwords.
Morphology, syntax, word order, cases.
Shared sounds and phoneme inventory.
Hangul → Chinese
Koreanic ↔ Sino-Tibetan
The 5 languages with the lowest linguistic distance from Korean:
A quick 3-question check between Korean and Cantonese. No signup.