Wúfǎ sùshuō de kǔchǔ wǎngwǎng shì zuì chénzhòng de.
The suffering one cannot express is often the heaviest to bear.
Tips
usage
苦楚 emphasizes inner, emotional pain or distress, as opposed to purely physical pain. It is more literary than 痛苦 (tòngkǔ) and carries a sense of prolonged endurance.