I have found a task of defeating great beastbug to be extremely hard, so i decided to make this guide to help out people.
How to Defeat Great Bug Boss
Finding The Bug
Here is how to find it: go to the town mentioned in mission description. From there, open a map and set up one pin in 2000 km to the west, and another one to 1500 km. Then, set two other pins in the 200 km to the top and bottom of the center between two initial pins. The beast’s lair will be in the top right part of this perimeter, you will find it easily.
You’ll need around 3000-5000 fuel for the travel and around 500-800 of water and food. Defeating the bug will give you additional 2000 fuel. I reccomend establishing an underground base in the west of near populated areas and building and upgrading a control center in it as much as you can so that the way back would be cheaper.
Defeating the Bug
I have defeated it with a party of mercenaries that i hired in the first village. They aren’t perfect warriors, i think only stats matter, not perks and you can reset stats of any character if you buy a “gene replacer” in the black market of late game cities.
Here is how i did it:
Whole party was leveld to maximum 10 lvl and everybody has been reset to 15-20 constitution and 20 perception and everybody was equipped best /almost best SUBmachine-guns (except main character: he had titanium crossbow IV, because it is most powerful weapon damage-wise).
You can get submachine guns of highest grade randomly by defeating level 9 robbers and bandits.
The reason is that submachine weapons have highest speed (that means your characters attack first) and still deal great damage (especially second skill (~450 dmg) – if characters have amazing happines synergy almost every turn they should have action points, but regular attack is good too (~350 dmg)).
The tactic is to focus ranged bug first and then main bug (he dies in 3-4 turns, depending on amount of times your ~90% hit chance imbeciles are going to be missing), healing characters that get damage immediately (corrosion is extremely dangerous), and then it is done. Did it first try after deciding to attempt the beast since last time he demolished my party when i didn’t have all submachines.
Your success will depend on how many times main bug will decide to attack your characters instead of buffing his own, which i think he prefers more, so never focus lesser melee bugs first.
For the reward you will get a one-time consumable that adds a whopping forty health points to a single character of your choice (it is used in same way as other healing consumables).
I have to remind you that the same boss you will be fighting to get that consumable will deal a 700 damage in a single attack to a row of your characters and a ranged bug corrosion damage deals 500, so you can imagine how much these 40 hp will come in handy in later game.
Besides that, if you decide to help Sword of Justice organization move from the desert (one of the story choices), you will be able to get the same quest to defeat the bug in one of the big towns north-east from initial SoJ base.
So, essentially, you can get two of these overpowered permanent buffs for your characters (defeating the bug bears no effect on the main story).