Peace be upon you. It is generally advised to avoid killing an animal unless it poses a threat. In such cases, it may be permissible to euthanize without causing suffering. However, there may be other prohibitions, such as ownership issues or legal concerns. According to Ayatollah Khamenei, it is better to avoid killing unless necessary. Ayatollah Sistani states that it is permissible, especially if the animal is harmful. May you be successful in all good.