Chthonians

Chthonians are giant burrowing worms—though not as large as Dholes—with tentacles for a "head". They are telepathic and can create earthquakes at will.

In the RPG...

Chthonians have 5 armour as well as 5 hit-point regeneration, which means that firearms are all but useless against them, though they aren't as difficult to take down as some of the bigger enemies. In fact, it would only take about 3 sticks of dynamite to kill one—assuming all three were thrown within the one round. 

    Chthonians do have one weakness, and that is that water injures them. However, it is unlikely that this could be used against them tactically, as it only does an average of 5 damage per 100 gallons, so it would take an average of 920 gallons (~3500L) to kill one. That's the equivalent of 17 drums. The 7e Malleus Monstrorum has removed these numbers completely, however, and just says that water does 1D6 damage per round "in large quantities".

    Attack-wise, Chthonians are extremely dangerous. They can either strike a victim with one of their tentacles, pick them up and drain their blood, or simply crush them with its immense bulk. The crushing attack has a 99% chance of killing an average Investigator in one go, and has an area effect of 5 metres, so could easily result in a TPK. Its tentacle attack only does an average of 7 damage, but it can get up to 8 attacks per round, so that could very easily stack up. If they're being drained of blood, an average Investigator will be dead in about 3 rounds. It should be noted that even though a STR vs STR opposed roll is not mentioned as an option to break free from being held, there is a 6% chance an average Investigator would succeed in one, so I would personally still allow the option.

    Chthonians also have some abilities up their sleeve that make it even more dangerous. First of all, they can use telepathy to control humans via opposed POW rolls. Given that a Chthonian has 90 POW, an average Investigator has a 80% chance of losing. Chthonians are also able to create earthquakes. An average Chthonian on its own is capable of creating a 0.9 earthquake (richter scale), which would not be felt at all, but others can add POW to increase the effect. As such, a "moderate" quake of 5 would only require about six Chthonians to partake.

In a video game...

Being large but not unbeatable, I think Chthonians would work great in a video game. As with the Dhole, they could make for an exciting chase scene as well, though with the Chthonians' speed of only 6 MOV, it would probably be on foot more so than a car chase... and would probably involve an earthquake.

In a film...

I think Chthonians would be great in a film. Though I've never read it, perhaps Brian Lumley's The Burrowers Beneath would work as an adaptation.