hey... finaly a post in my area of expertise!
I'm gonna assume that by biggest, most people assume how long it is and I'm also gonna stay in the realm of reality here... so the guy with the big bagua sword does not count... sure you
could use it in a real fighting situation, but only once because when you cut something with it, its so thin that it will bend very easily.... and what about blocking with it..? sorry... not gonna happen. That blade was designed not to hit anything and for forms only... you need some kind of shape in the blade to support the edge to make it stiff enough to withstand multipule cuts and blows....
the Europeans are usually considered to be the ones with the biggest usable swords in some quantity... and while asia did make some long blades... they are pretty rare and most were for cerimonial use...
this is mostly due to iron ore deposits... europe had lots.... asia does not... thats why we see the advent of iron and steel plate armor come in... so in asia the thinking was... "we only have so much raw material... why make one suite of armor when we can make many smaller blades..?"
and also to clear up the weight issue.... just becasue a sword was big does not mean it weights 20-80 lbs... most two-handers never weighed more than 7-8 lbs... most were in the 4-6lbs range for anything over 50"... example here...
Angus Trim 1592
and another from the makers Arms and Armor
16th Cent Danish two-hander
so... keep in mind when thinking about two-handers and other greatwords is.... is it made well..? sound hilt construction..? and most important... can I wield it
effectively.. that being a key word... you can make a sword as big as you want as long as you can control it.... if you can't... well... your a dead man and might as well be holding a lead pipe.
oh... and these swords were never meant to chop off horses legs or anything of such nonsense.... spears are better for cavalry.. two-handers were good at melee and believe it or not... spear formations.... they would wade in, knocking or cutting off spear heads as they closed ranks and decimated spearmen and anyone else in their path...
for further reading....
MyArmoury.com
and
Historical weights of swords
Best,
kokoro