The bad thing about using Cloud for that, though, is that he's probably already killed enough monsters to be taken out by "Everyone's Grudge" in one hit. If possible, you should use Cid, since he's probably the last character you got, and will most likely recieve the least ammount of damage from the Master Tonberry's painful counter attack (it's damage is based on the target's number of kills, I'm not exactly sure on the formula though).