In fiction, characters can harm others in many covert ways without being noticed. Here are some possible strategies: 1. **Psychological manipulation**: Characters can use psychological tactics, such as spreading rumors, creating misunderstandings, or leading others to negative emotions, to manipulate the other person's emotions and thoughts to cause them to harm themselves. 2. **Indirect harm**: Characters can take indirect approaches, such as putting the victim in a dangerous situation or deliberately withholding important information, causing the victim to encounter an accident. 3. **Use others**: Make others unintentionally become tools for harm, such as by provoking or manipulating others to attack the target, while the character himself remains clean. 4. **Disguise as a friend**: Pretend to be a kind friend or supporter, providing help on the surface, but secretly undermining the victim's ability with bad advice or misleading information. 5. **Slow erosion**: Take a gradual approach, such as slowly destroying the victim's self-confidence, social circle, or material foundation, causing it to gradually collapse without being easily detected. 6. **Hidden physical harm**: For example, drugs or toxins may be placed in food or drinks, or hidden safety hazards may be buried in the target's living environment, so that the victim is harmed without knowing it. Through these strategies, complex and deep characters can be created, and they can present multi-layered psychological struggles and motivations in their interactions with others, making the story more fascinating.