Blocking in ipv6 works roughly the same way as in ipv4, just that the scale is different. Instead of blocking something like a company's /24 or an ISP's /16 when they don't respond to abuse messages, you block the company's /48 or the ISP's /32. It'll vary per organisation how large a range they got exactly but you can see that in WHOIS. End users are no longer at a /32 (v4) but at /64 (v6), or some prosumers might have a /29 (v4) and /56 (v6). Same concept, just a different prefix length