The twin of How Dangerous Are Spikagi?, which concerned Spikagi. This question concerns their big blue twin:
It sounds funny, but it's not. These big blue bruisers are 4 feet 10 inches tall, with an egg-shaped body, two stumpy legs, and two flail-like arms and tail. They have the strength of a gorilla, proportional to their size, and their bodies appear to be made of some sort of blue, vulcanized rubber. This unique aspect of their physiology makes them extremely resistant to cutting, stabbing, or bludgeoning damage, to the point that they are impervious to conventional medieval weaponry (arrows, spears, swords, axes, warhammers, and the like) that hasn’t been specially designed or enchanted to overcome their defenses. Oh, and they're fireproof.
The position of their blobby eyes and frowny mouth reminds one of a frog, and this is actually one of their greatest weapons. You see, with their prehensile tongue and wide gape, they can actually reel in and devour an adult male, much like a giant frog.
They make up for this terrifying ability with their tongue’s length (which reaches up to thirteen feet), their speed (their top speed is 6 m/s, 13.4 mph for those used to that form of measurement, but they can sustain that indefinitely), and their intelligence. They have slightly below average human intelligence, like the stereotypical football jock.
They aren't exactly rare (see ProjectApex's answer to How Dangerous Are Ploppers? for why), so Whackagi form "tribes" of 11-22 individuals. These tribes work together well when they're defending themselves or competing against other tribes, but when all is said and done, Whackagi tend to go off and do their own thing. This "thing" is usually looking for fights (or food), fighting other Whackagi, setting stuff on fire (the mages don't know how they do it with flails for arms, but they can and will set things on fire), or setting up massive explosions using black powder they made themselves.
All that considered, I have to ask: How Dangerous Are Whackagi?
Specifications For Best Answer:
The best answer will analyze the lethality of a Whackagi (its ability to harm or kill medieval Europeans) and its CRD (Capacity to Resist Dying) to determine how dangerous it is (to medieval Europeans). CRD is based off a monster's durability, and how hard it would be for medieval Europeans with medieval weaponry (specifically medieval villagers, soldiers, or knights) to kill or harm that monster.
The best answer will also take the Rarity of Plops and Chompers into account, which have populations akin to rats in the wild. Chompers often eat Plop, just because they are there, and as stated before, 9 out of 10 of those Chompers will become Ploppers while the lucky one left will have a 50/50 shot at becoming a Whackagi.
Finally, the best answer will address whether some aspect of Whackagi makes them ridiculously dangerous or hard to kill. I want them to be a credible threat, but not overwhelmingly dangerous.