end, finish
竣 centers on bringing something to completion: ending a task or finishing a project. The meanings "end" and "finish" are two sides of the same idea of reaching a final state.
竣 combines 立 (stand) with 夋, which likely contributes the sound and the idea of completion or finishing. The exact historical development of 夋 is uncertain.
The left side 立 (stand) suggests something upright and settled, while the right side 夋 looks like a person finishing a task. Imagine standing up after completing a long job: 竣 means the end or finish.
For ドウ, picture finishing a long dough-making process: dough -> ドウ, and when the dough is ready, the work is done.