3 sentences

1. 他们的性格截然不同。

   tā​men de xìng​gé jié​rán​bù​tóng.

   Their personalities are completely different.

   Source: Dong Chinese Dictionary

2. 他的生理构造截然不同。

   tā de shēng​lǐ gòu​zào jié​rán​bù​tóng.

   His physiology is completely different.

   Source: OpenSubtitles

3. 面对这两个截然不同的选择，他感到十分为难。

   miàn​duì zhè liǎng gè jié​rán​bù​tóng de xuǎn​zé, tā gǎn​dào shí​fēn wéi​nán.

   Faced with these two starkly different choices, he felt very conflicted.

   Source: Dong Chinese Dictionary