I was once down $7000 on a yen position running bad, so I doubled down and ended up losing $21,000. However that position was hedged by a loonie (canadian dollar) position pointing in the opposite direction, and that leg made me $27,000 before the Euro position took away $8000 of it, leaving me $2000 down in all. 
The most money I ever lost on an “Overall” situation was "not taking a $24,480 offer for some S&P options that were to expire the following week, and were doing quite nicely at the time. However, an unfavourable non-farm payrolls report on the friday that same week (Jan 2002) crushed that position down to a zero (worthless) expiry. Technically, I lost $24,480 but I only paid $3750 for the position in the first place - so really I only lost the $3750…
The most I ever made in the futures & options markets was $7500 on coffee, $5750 on Soybean options, and numerous profits of around $2500 on everything from Gold to Crude Oil. It’s easy to make a nice profit - but it’s even easier to have the whole thing blow up in one’s face - but that’s why the derivative markets are considered “high risk, high reward” and are tantamount to gambling rather than serious investing.
On the Horses, I won £15,014.64 in February 2000 on a 25p each way treble bet. The proceeds got me the deposit I needed to finally get a mortgage after many years of “not having enough for a deposit” . These days, £15k would be small beer however. I’ve heard of people with £48k deposits being laughed out of the bank whilst applying for a mortgage!
I’ve had 3 winners in my regular trebles perms I do on numerous occasions since, but never exceeded that all-time best win for me there back in 2000.
The last time I had a nice return on the geegees was last October, landing £4500 for 5 places on an identical each way treble perm that landed me the £15k 18 years ago. It’s nice winning £4500 for no winners whatsoever, but I’ve yet to get five winners. My record is 4 winners - but I only had a tiny stake on it, so only won just over a grand for that one.
I don’t bet on the football, but occasionally have a bet on the politics. I had a tenner on @ 40-1 in the run-up to last year’s election when everyone was convinced Corbyn was going to lose between 50 and 100 seats… The price for “Labour to win 260-299 seats” was 40-1, and with them on 229 as it stood, I figured “Surely winning a mere 31 seats isn’t THAT hard?” They ended up winning 262, so I won a return of £410 by a gnat’s chuff you might say…
When I bet I rule out all short prices at the start, and then decide among the so-called “No Hoper” situations one can bet upon - which ones actually have a chance of coming to pass!