I am not sure, lol. Maybe 1 duck 500ib.
I think that the 500 1 lb ducks would have an advantage on the 500 lb duck because there is more of them and they can run rings around that big o duck who probably can’t move as fast because it’s so big thanks for your comment
Every fight games like boxing is always organised and scheduled. Weight is the most consideration between the opponents. So definitely if you do the maths, there will be a fight tooth and nails and no opponents would have won. Reasons, their is same weight both sides but only tactics will have knocked out the 1 duck with 500lb.
Thank you Hillary for sharing your comment

I think that the little 500 1 lb duckling would have a lot more advantage over the big o 500 lb duck it would definitely be slower and them little critter would run rings are that big o duck lol