Identifying scorpions:
 Non-venomous 
Thin-tail scorpions (families Scorpionidae, Ischnuridae). They have thin tails
and broad, well developed pincers. 
 Highly venomous
Thick-tail scorpions (family Buthidae).  They are characterized by thick tails
 and thin pincers.  The top image shows the highly venomous Parabuthus 
 transvaalicus 

The black emperor scorpion (Pandinus imperator) from western Africa is one of the largest scorpions in the world. In spite of its size, up to 20 cm and 60 grams, it is not so dangerous. Its poison is relatively weak and could be compared to a the poison of a wasp.

Flat Rock Scorpion Hadogenes troglodytes

Euscorpius balearicus female (Spain)
 
 

Opistophthalmus capensis