I find that with the Laser (sniper), the energy field (with the upgrade that converts enemy projectiles to YOUR projectiles) and Lightning (whichever upgrade) it is very doable albeit challenging, but it IS the hardest difficulty. Especially if you increase the rate at which the attacks activates, expand the energy field's radius, and of course, buying the upgrades in 'Research' before the level starts. Yes it will take several attempts, and you'll need to find which upgrades regarding speed, damage reduction, health regeneration, attack increase, element effects and so on best fit your playstyle (personally I don't normally bother with increasing my flight speed all that much. One upgrade for speed is normally plenty to keep the ones that chase you from catching you.)
But if the hardest difficulty is too hard....then simply don't play on the hardest difficulty. It has different difficulty settings for a reason.

I beat the game with pretty much 0 upgrades through the passive menu. It mainly comes down to which upgrades you choose and being able to just dodge and kite the final boss at the end. It was a very slow, slow kill but I think maybe 10 minutes or so I killed the boss.

我的玩法是主武器選聚能炮或是副武器選光波，天賦選操作天才或計畫完善＋瘋狂，進入遊戲後就是看運氣撿到消除子彈給聚能炮或是光波，之後聚能炮的話就是多增加射擊數量和範圍，光波就只要選擇持續發光的效果就好．最後一個武器大多是選護衛機靠數量多的特效去打

Noob

Grind money at lower levels first and research some more upgrades. Take Lightwave as your primary weapon to make it easier cause the left upgrade tree absorbs bullets and on max level even reflects it.

Pick Recycle mods, if you have researched the special extreme mod upgrade (which costs 20k iirc) having 3 of those will allow you to sometimes gain mods from random mobs and not just elite. Now if you're lucky enough, you can install 3 of those for each weapons and it will be raining HP, battery, and magnet drops.

Pick passive upgrades that will give you more dmg / atk spd / crit dmg the more annihilator you have ready and then slot in Energy Body as one of your talents (in the Gears menu), you will benefit from all the bonuses. Also if you have Recharge mods unlocked pick those too, having 3 of those will give you 2 extra annihilator slot and is cumulative to each weapons you've installed so if you have 3 for each weapons you'll gain 8 extra annihilator. Multiply that with the bonuses you get from those passives.

If you're struggling to survive, get more HP and damage reduction. And get more revives so you can have more attempts. Some passives even gives you extra damage for dying so you can deliberately destroy yourself for some bonus dmg.