Looking on the internet deeply has found these results:

Do you understand? is the most popular phrase on the web.

Do you understood? 13,860,000 results on the web	Do you understand? 1124,000,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
Understood? My territory within these lines. Understood? That's fine. Under no circumstances do you fail in this endeavor, or our entire night is null and void, understood? Just follow my orders, understood? This is our investigation, understood? Do you understand what I understood?	"Do you understand?" Like she's talking to a child. Nobody kisses me, do you understand? "Indeed, you may invite your friends to tomorrow's party. Only remember to return home before dark. Do you understand?" I can't be around anyone, do you understand? Yes, we won't be together Do you understand? But, nothing for the Smiths, do you understand? Responding politely is how it should be, =but you must draw the line.= =Do you understand? Until they're shinning... do you understand?

Do you understood?

13,860,000 results on the web

Do you understand?

1124,000,000 results on the web

More popular!

Understood?
My territory within these lines. Understood?
That's fine.
Under no circumstances do you fail in this endeavor, or our entire night is null and void, understood?
Just follow my orders, understood?
This is our investigation, understood?
Do you understand what I understood?

"Do you understand?" Like she's talking to a child.
Nobody kisses me, do you understand?
"Indeed, you may invite your friends to tomorrow's party. Only remember to return home before dark. Do you understand?"
I can't be around anyone, do you understand?
Yes, we won't be together Do you understand?
But, nothing for the Smiths, do you understand?
Responding politely is how it should be, =but you must draw the line.= =Do you understand?
Until they're shinning... do you understand?