I’ve put everything I need to run a Dungeons & Dragons 5th Edition encounter on one page, with enough space for 40 monsters (4 different monster types, and 10 individual monsters for each type).
This doesn’t include every stat for every monster; just the stats that I need for 90% of my encounters: Hit Points, Armor Class, speed, initiative, attacks (attack bonus, average damage, damage roll, and damage type/special options), and special abilities.
There’s also an initiative tracker on the side, numbered from -5 to 25. Just write down where each creature is, and you can just glance down to see who’s where. There’s even a round tracker.