Did you know underleved still exist nowadays ?
I didn't.
Thanks to ProfessorRex here a list of the non event ones in SV :
-Tera Poison Sliggo (lv30) in wild tera
-4* Tera Raid Bisharp (lv45)
-4* Tera Raid Drakloak (lv45)
-4* Tera Raid Zweilous (lv45)
And here all I found in Grand Underground at level 16 in BDSP (with National Dex and 1 badge)
Spacious Cave
Raticate
Gloom
Venomoth
Primeape
Rhydon
Houndoom
Mightyena
Crawdaunt
Sandslash (Pearl)
Shelgon (Pearl)
Graveler
Golbat
Machoke
Grassland
Poliwhirl
Weepinbell
Skiploom
Cacturne
Ariados
Ledian
Purugly (Pearl)
Skuntank (Diamond)
Fountain
Dewgong
Gastrodon
Rocky
Pupitar (Diamond)
Lairon
Camerupt
Vibrava
Volcanic
Magcargo
Swampy
Weezing
Tangrowth
Dazzling
Banette
Dusclops
Kirlia
Some remain mystery (if you can really get them underleved) such as the ones where you need Surf (Lanturn, Tentacruel, Whiscash) or the Icy Cave (Walrein, Glalie, Sealeo).
I don t think it s possible, but maybe lv33 Glalie/Walrein can be a thing at least ?
Did you find any other ones in BDSP/SV/ZA ?