由【yóu】

由 + person, before the verb, says whose job something is. The task goes first as the topic; 由 brings in who does it. It is neutral to formal – common in work, school and official announcements.

来 often comes after the person, with no change in meaning: 由李明来完成.

由 or 被

被 says something happened to the subject, often something unwelcome. 由 says who has been given the job. A broken cup takes 被; an assigned task takes 由.

• × 杯子由他打破了 → 杯子被他打破了

Where it goes wrong

The person goes after 由, not in front of it as the subject.

• × 我由负责这件事 → 这件事由我负责

由 also appears in 由于 "owing to" and in 由…组成 "made up of". Those are separate points.