A scorpion but is much larger than its normal counterpart. Pincers and a tail of numbing toxins make them formidable foes.

As you approach the overhang, you notice the pincer of a giant scorpion. - Taron's Trophy (RPA-ADV2) 

Giant Scorpion venom, injected from its barbed tail, has a temporary paralyzing effect:

Instead, there is a massive, angry welt on its abdomen. The poor animal froths at the mouth, clearly the victim of some horrible venom.

After a few more moments, the venom seems to wear off. - Taron's Trophy (RPA-ADV2) 

When first encountering the pig with a spot like a black swan outside Jolev, you discover a Giant Scorpion using it as bait for larger prey:

• Lie in wait to slay the monster.
• Alert the Giant Scorpion of your presence:
  • Fight well and finish it off spectacularly.
  • Eventually defeat the monster after receiving a sting yourself.

You defeat it regardless and save the pig.

In the city square, a Giant Scorpion and Owlbear have both escaped Taron's Arena and approach a distracted Lady Emilia Duntum, should you have met her earlier that day and let her walk home alone;

• Slay the beasts and seemingly save her life.
• Leave the area in defeat; Emilia disappears.

A giant scorpion enters the arena from the western gate, and the audience cheers. A few of them scream, “Betsy!” at the top of their lungs. The Grandmaster’s voice booms over the din of the crowd: “Big Betsy, as she is lovingly known, has long been a fan favorite at the colosseum,” she explains. “If she wins, this will officially be her 100th kill in the arena.” - Tome of Encounters (RPA-SQ1)

• End Betsy's career, to the dismay of the crowd.
• Instead of ending you, Betsy lays a clutch of eggs in the ash.