Umm is home world that strong? I thought except for the Bentusi everyone is around mass effect or maybe Star Trek level at most.
Homeworld's pretty strong but they don't map perfectly to other factions, a lot of their stuff is kind of orthogonal. Note that The Beast was able to curbstomp the Bentusi, which is what we're looking at for this Vs. Debate.
Generally, their ships are slow, with low-double-digit Gs of acceleration at the top and single-digit Gs for their biggest ships. Most factions can outrun them.
FLT speed, though, is really fast. The Kushan traveled across most of the galaxy, constantly having to stop and scavenge, mine, or fight for their lives, and did it in about six months.
They have no shields but the manual goes into a great deal of detail on their armor, which makes heavy use of composites, reactive components, and spacing. Basically they don't miss a trick when it comes to maxing what they can get out of armor.
Power generation of a single hypercore is stated to rival the total output of a main sequence G-type star in
Deserts of Kharak. That said there was some retconning going on, in
Homeworld those cores were just power plants the Kushan reverse-engineered from the
Khar Toba. The Kadeshi had the exact same cores, it's kinda a plot point there since the Kadeshi had reverse-engineered the exact same model of ship and shared a common ancestor with the Kushan.
Homeworld 2 changed that to them being ancient progenitor artifacts which is really hard to square with the Kadeshi having multiples of them.
Firepower is decent but not the highest in the multiverse. Even their strike craft are packing, essentially, battleship-scaled cannons except they're
Gatling. These weapons are all but useless against larger craft. Fusion warheads are only really effective against Frigates until At the top end, we have a ship whose main weapon requires
three of those hypercores to supply it with enough energy...
Research and Construction speeds are a thing that would make Minecrafters weep with envy. To build on what
@Aldarion said, we know Kiith Somtaaw rented the Mothership's fabricator for six months. First, they designed and built their own mothership, the
Faal-Corum. During the construction process they did enough research to design a second, much more advanced and modular Mothership, and used that knowledge to build the
Kuun-Laan. Finally they instead built a top-of-the-line science vessel, the
Clee-San, with their remaining fabricator time. Missile Destroyers are flat-out stated to be manufacturing new missiles on the fly, they can "dump the tubes" and then manufacture a fresh supply of missiles in under a minute. Just in general, if they have the resources, their manufacturing ability is "yes."
In general, their design philosophies can be a bit wonky. Homeworld ships are usually very specialized, they tend to plan on having a large number of ships with multiple layers of screening elements screening their screening elements. This makes sense given their crazy build speeds and ability to make stuff as needed, but also means that, f'rex, a Battlecruiser entirely by itself and lacking its screen can be highly vulnerable to being swarmed with fighters.
Their AI and Automation is about as high-end as it gets without having fully autonomous droid ships. A hundred people can operate a ship the size of a small city. The manual calls out how boarding parties have to hit the enemy ship with a massive spam of computer viruses and fight constant counter-measures to try to keep a ships automated systems locked down while they take it over.
Everybody in Homeworld is loot-happy to an extent that makes the Orks look like ascetic monks. Salvage Corvettes stealing everything that isn't nailed down is mimetic. The Beast infects and subverts everything it comes near whether an enemy ship or organic brains. The Junkyard Dog stealing capital craft and whatever the ancient ship is that mind-controls vessels at range are hazards the Kushan have to deal with. Basically stealing everybody else's ships and reverse-engineering everybody else's tech is SOP for every faction in the setting.
TL;DR: Overall the traits that are going to let The Beast roll through the Imperium are its Blazing FTL speed, absurd manufacturing/reverse engineering, and ability to turn anything at range into more of itself with Infection Beam. Its speed and spread rate gives it good odds of being able to invade and take over large chunks of the Imperium faster than the Imperium is even able to spread news of what's happening. The Beast can corrupt any known organic or physical material it encounters into more of itself. It also absorbs the crews of ships it eats, allowing it full access to their memories which it has used to great effect. It can integrate any tech it reverse-engineers and design new infected ships to use that tech. It has a super-genius intellect with great cunning and no sense of fair play, and was able to piece together literally every race and major event in the galaxy from stray radio signals when it was still confined to a broken beacon, and stated it knew "More about your race than you do." It can throw down entire fleets in a matter of days, every one of which carries more Beast virus and can spread it further.