Solution-focused therapy would be the most effective treatment approach for this client due to its focus on finding solutions rather than dwelling on past issues. This type of therapy involves creating strategies over multiple sessions that help individuals break down their goals into manageable steps; by doing so it encourages them to think about how best to address their immediate concerns in order to move towards long-term self betterment.
For the second client, a 50 year old male who experienced childhood trauma and now struggles with depression and suicidal thoughts, I would diagnose him with Major Depressive Disorder (MDD). This diagnosis is based upon his low mood lasting for at least two weeks along with other classic symptoms associated with MDD such as significant weight loss/gain or having no interest in activities he used to enjoy.
In this case Cognitive Behavioral Therapy (CBT) would be more beneficial due to its goal of helping individuals identify ways they can change negative thought patterns or behaviors which are contributing to their depression. For instance, CBT may encourage this individual find healthier outlets—such as physical activity or creative endeavors—which replace any unhealthy coping mechanisms like substance abuse that he may have developed over time due his past traumatic experience.