Cid Highwind is another favourite of mine in FF7.
Like Barret, he's incredibly foul mouthed, able to churn out 4 letter words multiple times in one sentence, This spans from his backstory.. which I found to be a perfect set up for who Cid is, and why Cid is the way he is.
Cid was set to be the very first man into space, which had been his lifelong dream. His assistant Shera spotted a malfunction in the ship, moments before the ship was set to launch (actually, during the countdown), so she set out to fix it.. The room she was in was set to burn on flight and she couldn't leave, she would surely be killed. So Cid makes the decision, mere seconds after the ships launch to abort the mission, crashing the ship... leading to the space programme to be abandoned.
Up until meeting the Cloud and the party, Cid spent his days with cynicism towards pretty much everything, for not fufilling his dream. And though he constantly shows anger, it's obvious that deep down he's kind-hearted.