彻底说再见，英语是：Say goodbye thoroughly.
详细解释：
say 英[se?] 美[se]
vi. 说， 讲 表明，宣称 假设 约莫
vt. 表明 念 说明 比方说
n. 发言权 说话 要说的话 发言权
[例句]I would just like to say that this is the most hypocritical thing I have ever heard in my life
我只想说这是我这辈子听说过的最虚伪的事情。
goodbye 英[?g?d?ba?] 美[?ɡ?d'ba?]
n. 再见
[例句]He said his goodbyes knowing that a long time would pass before he would see his child again
他道了别，知道要过很久才能再见到他的孩子。
thoroughly 英[?θ?r?li] 美[?θ?：r?li]
adv. 彻底地 认真仔细地 完全地 非常
[例句]He was surprised to find his room thoroughly cleaned and everything arranged in perfect order.
他惊奇地发现房间被彻底打扫了，一切都布置得井井有条。