Crocodile is the first villain that easily beats Luffy (twice) while Luffy survived due to Robin's interference and luck. However, one of the comments on his devil fruit power struck me.
Chapter 178: Wikia (Anime Episode 110) Emphasis mine
Luffy is astonished at Crocodile's power while Crocodile comments that he does not just possess his devil fruit ability like some people, he mastered it and demonstrates this by creating a hole of quicksand.
Crocodile can absorb moisture and convert anything to sand, i.e. he can permanently convert something to sand. He also completely annihilated the palace garden. He can create large sandstorms which can run for days. He can control sand in the city which can cover it like a fog. These abilities seem to point in a direction outside the limit of Logia powers.
We also know Crocodile knows about awakening. In Chapter 544 Crocodile is the person who tells us about the awakened Zoan type Jailors
Crocodile then reveals that the Jailer Beasts were all "awakened" Zoan Devil Fruit users, saying that their extreme physical endurance and recovery point were their advantages. Crocodile states that the other three would soon awake and that the Boss of Hell would be arriving soon.
So is there some reference about Crocodile and his DF powers? Maybe something Oda has said in SBS, about crocodile, limits of Logia powers or Awakened Devil Fruits.
Other Observation: Akainu and Aokiji may have awakened DF's since they converted Punk Hazard into Freezing side and Burning side permanently. (Also Akainu burning Ace). Enel may have a hand in the island that is permanently spewing lightning etc.