Miss Ellie appears to be the toughest. She was certainly a formidable character and dare I say even bullyish at times so if that's being tough, then yes. Punk said Jock was tough but fair. I'm not sure him or Miss Ellie were particularly fair.
All the women had tough sides, maybe not consistently but they did. They could also be weak and vulnerable, even Miss Ellie. Donna was fairly tough but that caused problems with Ray.
Sue Ellen wasn't whiny, at least she kept her problems quiet until exposed by JR or prodded by Bobby. She hardly confided in family members and when she did it was too late because she would be already drunk or deeply depressed. That's not wallowing in self pity, there's a difference. It's also not the opposite of tough.
Rebecca and Patricia were probably "tough."
Sue Ellen was really tough at times, she had to be to handle JR and at times she handled him brilliantly.