You will start by yourself against Weigraf. Make sure Ramza looks like this:
Squire Two Swords Auto Potion (only x-potions in storage) Item At least level 26 or 27
Weigraf is dangerous due to his large health, damage, and counter ability. Simply run away and use potions when necessary. When ever it is your turn, use accumulate until your strength is 50, yell until your speed is 50, and get your brave to 100. When your strength and speed are at 50, go behind Weigraf and with one lucky strike, you'll defeat him.
However, he then turns into Velius. Just get near him too and with 2 strikes, he'll be finished, and you'll have conquered the hardest fight of the game.