Think of a set of scales with two pans sitting level, and a hand pressing down on one of them. Nothing is broken. One side has simply been given more weight, so the whole thing can no longer hold itself up. That is unbalance: a knock, a push, or an extra load moves the weight to one side, and steadiness goes. The same picture is then used for things you cannot touch, like a friendship, a report, or a person's mind.
Wiktionary records unbalance as un- plus balance, and traces balance back through Old French to Latin bilanx, a scale with two pans. The idea of two sides that must weigh the same is inside the word from the start, and un- simply undoes it.
Wiktionary 記載 unbalance 是 un-（相反）加 balance，而 balance 可以經由古法文一路追到拉丁文 bilanx，也就是「有兩個秤盤的天平」。「兩邊要一樣重」這個畫面本來就在字裡面，un- 做的事就是把它推掉。
Wiktionary etymology tree supplied in packet (kaikki:3f6f69a190036ae4:1536770802:7695): un- + balance; balance < Old French balance < Vulgar Latin *bilancia < Latin bilanx
From the picture
看不見的那一邊變太重
把「重心偏掉」從身體搬到摸不到的東西上。關係、團隊、文章、畫作，甚至一個人的心，都可以想成有很多部分互相撐著。只要某一邊突然變重，東西沒有壞，但整體就歪了。
verb · C1
To spoil the balance of a situation, a relationship, or a piece of work, so that it is no longer as good as it was or could be, usually because one part has been given too much weight or too much room.
使失衡
verb · C1
To knock or push a person or a thing so that they are no longer steady on their feet or on their base, and are likely to fall over.
使站不穩
以下是外部詞典記錄的用法，原文照列，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
unbalanceverb/ʌnˈbæləns/
To cause to be out of balance.
資料來源：英文維基詞典 English Wiktionary（CC BY-SA 4.0）。 原文照列，未經改寫。