Learn Mandarin Grammar: The difference of 彻底(chèdǐ)and 完全:

彻底(chèdǐ= complete) is deeper than完全(complete).

Example 1:

We must solve this problem completely.

a. 我们必须彻底(chè​dǐ)解决这件事。(更深刻(shēn​kè=deep))

b.我们必须完全解决这件事。

Example 2:

What he is not satisfied is that the work is not completely completed.

a.他不满的是工作没有彻底(chè​dǐ=completely)完成。(更深刻(shēn​kè))

b.他不满的是工作没有完全完成。

Example 3:

He always washes the dishes completely.

a. 他总是把菜彻底洗干净。(更深刻(shēn​kè))

b. 他总是把菜完全洗干净。