Generally, 完 = finish ＝ usually follows a verb 结束 = end = is usually the verb 我吃完了饭，就去睡觉 (i will go to sleep when I finish eating) 我做完功课了 (I have finished my/the homework) 游戏结束了 (The game has ended) 影片结束了 (The film has ended)

结束is more professinal,这部电影结束了 完is oral电影演完了 Usually,完 can't be used as "end"singlly,it needs a verb

完 is adverbs of degree and adjective 结束 it's a verb and adjective.

完：finish 结束：end / over / done