"If your chart has no y-axis I will ask about it." Now the full lecture. Metrics that predict churn, ranked:
Support tickets per account, trend (rising tickets + falling logins = gone in 30 days, every time). Time-to-second-value (first value is onboarding, second value is habit; the gap between them is the churn window). Seat utilization (3 of 10 seats active at month two = a cancellation wearing a subscription). Invoice surprises (the number-one "reason" in exit surveys that means "we never looked at the bill until today").
Vanity accompanying each: NPS (measured yearly, churns monthly), total signups (births, not health), and my beloved enemy, the y-axis-free up-and-to-the-right.