HR covers work that has almost nothing in common from one role to the next. A recruiter fills roles, an HR business partner advises leaders through restructures and performance cases, a reward specialist runs benchmarking and pay reviews, and an HR generalist in a 60-person company does all three before lunch. "HR manager" tells the reader none of this, so the CV has to.
The second thing to settle early is scale, because it changes what every other line means. Supporting 40 people in one office and supporting 900 across four countries are different jobs with the same title, and the second involves works councils, local employment law and a payroll you do not personally run. Headcount, sites and countries belong near the top of every role.
The third is confidentiality, and it is where most HR CVs go wrong. Your best work is often a case you cannot describe: a settlement, a dismissal that held, a grievance handled so quietly that nobody outside three people knew. The answer is not to omit it — it is to write the shape and the outcome without the identifying detail, which is a skill the reader will recognise immediately because it is one they use themselves.