In chapter 1, Rat is talking to Mole about the creatures who live in the Wild Wood. One of those creatures is "dear old Badger." Rat tells Mole that "nobody interferes" with Badger and then adds, "They'd better not." The implication here is that Badger is perhaps a loner who doesn't like the company of other animals. When Rat says, "They'd better not," this sounds like a threat, which also implies that Badger is, or can be, rather fierce. However, Rat still refers to Badger as "dear old Badger." The "dear" here implies affection, so perhaps the other animals, including Rat, have simply gotten used to Badger being a loner and like him nonetheless.
A little later in chapter 1, Badger is described as having "a stripy head, with high shoulders behind it." The "high shoulders" indicate that Badger is a broad, physically imposing character. In combination with Rat's earlier warning that other animals had "better not" interfere with the Badger, this physical description gives an initial impression of an intimidating, perhaps even menacing character. Badger approaches Rat and says, "H'm! Company," and then "disappear[s] from view." The impression given here is that Badger is grumpy and maybe a little rude. Rat, however, seems used to this kind of behavior from Badger and simply remarks, "That's just the sort of fellow he is!" Rat also says that Badger "simply hates Society!" This confirms our initial impression that Badger is a grumpy loner.