Where to Find and Catch Karrablast
From Pokemon Go Wiki
Karrablast are found and captured in Nest and Habitat locations.
Nests
Karrablast Nests are locations that consistently spawn Karrablast.
Habitats
Karrablast Habitats are spawn locations where Karrablast is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: