Blackberry liqueurs come in a variety of types, each with its own character. Stick to the top shelf with fruit liqueurs; the lower-quality offerings are often artificially flavored and, in the US at least, often made with high-fructose corn syrup.
Blackberry liqueur is fantastically easy to make if you live in a part of the world where blackberries are abundant. If you’re so blessed, search on SeriousEats.com for their blackberry brandy recipe – it’ll blow your socks off.