Well can do stats but they won't tell you all that much - and there are various measures of size even within what Ive done...
largest trade I've ever done in one hit (in absolute terms) - around $1.7 bln or thereabouts.
Largest price I've had to make as a market maker, on a risk transfer basis, around $200m or thereabouts.
Largest trade I've ever done (as percentage of average day's market volume) - ard 500% (in an obscure currency and it took basically three days to get out of the position). Not large at all in absolute terms, but still meaningful.
Most volume I've executed in any one day - no idea but probably around the $ 8 bln mark but that really is a meaningless stat as there would have been a ton of swaps in there for a start.
Biggest f**k up trade - as directional pointed out I did have a large out trade one day a few years ago when I hit the wrong side of the price in cable and bought rather than sold £50m, making me effectively accidentally long £100m or around $170m at the time (and yes, my voice did go up an octave when I had to shout over to the chief dealer that I had had a little bit of a whoopsy, Frank Spencer style).
But none of this tells you the first thing about whether I'm actually any good or not, what trades made money, even WHY and WHEN I made those trades (they weren't all prop positions for a bloody start). All it tells you is I'm a wholesale trader and I've been round the block a couple of times.
Fwiw there's plenty of better traders out there than me, and I'm sure there's plenty of em on this site too. The size becomes less meaningful the longer you do it (most of the time)
GJ