I'm agreeing with PK Gaming. There are a ton of Pokemon in the OU meta game that sometimes require something to be sacrificed or to take a hell of a lot of damage in order to deal with a threat. I agree that Kyurem-B may not have many counters, but why for that reason should it not be allowed a fair chance in OU?
Think about it this way, coming off of what PK said about RP Landorus. If something like a Heatran comes into a RP Landorus, and the only thing on the team that can revenge kill is your Mamoswine, then Heatran or something else on the team has to be sacrificed in order for the free switch to Mamoswine. However, even then Landorus can still switch out. With Kyurem-B however, CB Outrage will ensure a KO, but at the same time ensure Kyurem-B to get revenged killed as well. Same goes with any set up sweeper like RP Landorus. Some big examples Breloom, who can force a switch with Spore AND sometimes OHKO with Mach Punch, sometimes leading to 4-6 already.
A Pokemon should not be banned due to a lack of a solid (key word) counter, but a check is a different story, which there's plenty of those out there for Kyurem-B. A few examples of something that was uncheckable, or lacked any reliable checks were Speed Boost Blaziken and Sand Rush Excadrill. Kyurem-B may not have reliable counters going for it, but should that really be the one reason as to why it should stay locked up in Ubers when there's a variety of checks out there?