The two most impressive speed feats for the Shrike(imo) are:
1. When Rhadamanth Nemes is phase shifted and in "fast time"(phase shifting causes her to be slightly displaced in space-time, while "fast time" is an ability that allows her to move massively faster than light), the Shrike seems to suddenly appear in front of her. The first sign she has of this, is that it suddenly becomes darker, something she states should be impossible while in "fast time". The Shrike then proceeds to essentially rip her apart. This is also an impressive strength feat, since her durability while phase shifted is insane. Earlier, she is blasted by a sustained energy beam from a space ship, and buried in molten rock, and she comes out of it completely unharmed.
2. When Fedmahn Kassad was wearing a suit that replicated many of the Shrike's abilities, it is described that he saw a beam of laser as a static(non-moving) line in the air. Despite that speed, the Shrike appears to Fedmahn Kassad, as if it is simply appearing and disappearing in different spots on the battlefield.
On top of it's raw speed, the Shrike has time manipulative abilities, which allows it to essentially slow time for itself, similar to what Zoom does to make himself super-fast.
Additionally, the Shrike can travel through "The Void Which Binds", which is Planck Space that connects all of space-time, allowing it to effectively teleport to any point in time and space, instantaneously.