>>2724265Close, but not exactly all there either
Badges are both offense and defense. The more badges you have, the more defense you have against lines being sent to you, and the more lines you send when you complete them. They work by just adding a % bonus (25, 50, 75, and 100) to the lines you "send" which both clears lines in your queue and sends more lines to the enemy.
Having more badges is always a good thing because tetris 99 has anti dogpile mechanics (there can only be up to 12 grey lines queued up at a single "time", so you can wait on clearing lines until the enemies are done sending stuff over before you can counter attack) among other things. It's why if you're pretty good, 1v98 is easier than normal tetris 99, because you're the only one getting badges
The guy was pretty good for being able to keep up with Suisei with zero badges while Suisei had 4, and with enough player skill and good game planning, you can mitigate and retaliate against someone like Suisei who mostly specializes in digging at the final stages of the game instead of setting up discrete attacks.
