Uber Mob Battle Strategy
Some of the easiest and most powerful weapons to obtain early in the game are the Antanium Weapons (Spear, Sword, and Maul). Antanium ore can be found in planets as early as Alba, albeit a bit rare, deep underground. All Antanium weapons have a durability of 1,280, a range of 4 blocks, and a solid 2.00 of their specific damage (with the exception of the Antanium Spear, which only has 1.80 damage) What makes this an excellent weapon to use against uber mobs is the fact that it has .20 life steal and with the very fast rate of clicking when attacking a mob, you will deal massive damage and take practically no damage in return.
An excellent alternative is the Ivory Sword. Its ingredients are 4 Ivory Bones and a single Gold bar. Ivory bones are very abundant on the surfaces of planets Yuca and Tor. Destroying bones found on the surface will yield one or more ivory bones and you can very easily craft an Ivory Sword from all of them.
 Areana Preperation
Place a bed in or near your arena to set your spawn. This way if you die, you will respawn next to the boss and your items. Make sure that any surrounding caves around you are lit up with torches as Uber Mobs have the ability to destroy blocks around you. If an Uber Mob breaks its way into a dark cave, you might get swarmed with mobs that will heavily distract you from the Uber Mob and potentially kill you. Likewise, an Uber Mob can burst an acid or lava pocket and cause the them to start pouring. Worst case scenario is that you kill the Uber Mob above a lava flow and burn its items away. Lastly, an Uber Mob might destroy the blocks that are above a huge cave and you could potentially die from fall damage. With these reasons stated, it is imperative that you check your surroundings before you start a fight.
Make sure the place is relatively flat with a few elevated blocks. Fight the Uber Mob a few blocks in an elevated position to reach its minions more easily and kill them more quickly. Also remember to make a wall opposite to where you are in order to corner him and allow yourself to spam click the Uber Mob until it dies. Simply put, it's ideal to fight the Uber Mob in a closed space which has enough space to retreat when needed.
 Cheese Strategy
If you don't want any challenge, or just want to get the loot, you can simply craft a few potions of invisibility. All mobs in the game, including bosses, do not perform any actions apart from regular wandering if you are invisible. Thus, just hit the boss to death during your invisibility time. The most easy way to acquire potions of invisibility is to make them yourself, with 2 rotten meat + 3rd reagent.