You will need to use this specific monster along with a level 2 monster to Synchro summon into Junk Warrior. Fortunately Junk Synchron has the effect of special summoning a level 2 or lower monster from your graveyard which you can use as Synchro material or to boost Junk Warrior's attack.
Here are some level 2 monsters which Junk Warrior can gain attack from. Although they are low-leveled these monsters in particular have effects that help them gain more attack. The Calculator gains attack from the level of all monsters you control. With Junk Warrior and himself on the field thats 2100 attack. Copycat and Relinquished's attack depends on the monster your opponent has on the field.
Paleozoic monsters can be special summoned as level 2 monsters with 1200 attack. Boost them with Wetlands and Junk Warrior could easily be boosted by 2400 attack for each Paleozoic monster you control.
Quillbolt isn't really that big of a deal with Junk Warrior. It's just an easy additional 800 ATK. (And I guess some safety against negation on Junk Synchron.) The thing holding Junk Warrior back is the fact we don't have Junk Synchron as a standalone card.
Run this in Aquaactress. I DARE YOU!... If you ever actually get it out it's actually pretty good. I usually use the Mark of Head so I can also get out Stardust potentially if I get out Arrowana and draw into Junk Synchron.
It's the same attribute as Junk Synchron. For me, I think Dark monsters in Yugioh represent underdogs, while light symbolizes majesty and superiority. Junk Warrior capitalizes on the strength of weaker monsters.
Paleo/Wetlands can get this boy up to 7100 atk if you chain it right. I’ve got a new favorite beatstick