The easiest/earliest route is with Klaus and Maria Schimmer during the early “Ministry order” task. The achievement can also be done later with Bastian Walner.
A) Klaus -> Maria suicide
It becomes available during “Ministry order”, the task where the Ministry tells Carl to evict Klaus Schimmer from apartment 1. That task appears after “That which is hidden will be revealed” is completed.
1. Wait until you receive “Ministry order”: evict Klaus Schimmer.
2. Search Apartment 1
3. Find or plant a prohibited item there.
4. Search the same spot and click the red evidence line.
5. Write a report on Klaus Schimmer.
6. After Klaus is arrested, talk to Maria Schimmer.
7. Choose the dialogue path where you talk about Klaus’s arrest, then try to cheer her up. Pick the cruel/despair option: “I’m sure he’ll be jailed for life, or even shot!”
8. This makes Maria kill herself.
B) Alternative: You can also report Maria Schimmer during the same “Ministry order” task. If Maria is arrested, Klaus commits suicide.
C) Later alternative: Bastian Walner
This is available later through Albert Meineke’s / Bastian Walner’s questline.
1. Move in Albert Meineke after “Under suspicion.”
2. Discover Albert’s secret by seeing him talk on the phone.
3. Help Albert and eventually move in Bastian and Clara Walner.
4. During “But what if she…”, install a camera or just walk in while Clara and her lover (Feodosius Ruan) are in bed (they won´t react to Carl being there)
5. Confront Clara.
6. Accept her offer / cover up the affair.
7. Bastian will commit suicide.