Mr. Punctual

Mr. Punctual is an Achievement in Halo Wars that is unlocked when the player completes all Campaign missions under Par Time on Heroic or Legendary difficulty.

It is worth 15 Gamerscore.

Par Times
Alpha Base: 5 to 12 minutes.

Relic Approach: 15 to 30 minutes.

Relic Interior: 8 to 18 minutes.

Arcadia City: 21 to 23 minutes.

Arcadia Outskirts: 21 to 35 minutes.

Dome of Light: 15 to 30 minutes.

Scarab: 12 to 24 minutes.

Anders' Signal: 18 to 30 minutes.

The Flood: 18 to 30 minutes.

Shield World: 23 to 32 minutes.

Cleansing: 20 to 30 minutes.

Repairs: 8 to 18 minutes.

Beachhead: 20 to 60 minutes.

Reactor: 15 to 30 minutes.

Escape: 20 to 33 minutes.

Tips
The easiest way to get this achievement is to complete all levels under Par Time on Heroic with all helpful skulls active. (Catch, Sugar Cookies, Pain Train, Bountiful Harvest and Emperor)

However, it is not recommended to use Boomstick as it can have negative effects such as blowing up your own units when at close proximity.