The expression "putting arm on" typically means using force or coercive tactics to achieve one's goals. In the context of interpersonal relationships or negotiations, this approach can be seen as aggressive or even bullying. Therefore, antonyms for this phrase would include more diplomatic or collaborative tactics such as negotiation or compromise. Other antonyms might include peace, calmness, respect, and empathy. By fostering mutual understanding, respectful communication, and empathy, individuals and groups can achieve their goals without resorting to harmful or abusive behavior. Ultimately, using positive and constructive strategies to reach common ground can result in healthier and more productive relationships.