im gonna have to go with otto destruct and klunk. But those are mad by high impact game and i think they make there bosses unfairely hard. So instead i choose drek because u cant srafe so it makes in awkward. Nefarious was easy after abillion times of beating that game haha.
Drek. Without a doubt, Drek.
I didn't have the RYNO when I fought him, so I had to try over and over and over and over and, well, you see where I'm going with this.
Managed to beat him, though! (After the 23rd attempt)
Drek is making me ragequits!, tough i did sucseed finish him off with… yes…. ZE WRENCH! 
it took me about a couple of 200 devastator rockets, and i don't know how many blaster ammo
otto is even worse if u dont beat him by the third time your scrued because you need mad bolts for the pda.
otto is even worse if u dont beat him by the third time your scrued because you need mad bolts for the pda.
No he isn't just keep spamming the schock barrier and R.Y.N.O. 
Besides, klunk is easy if you know the moves
i didnt have the ryno and still havin baten klunk
The hardest boss for me was Otto Destruct in Size Matters. I had to collect a lot of bolts just for the PDA, so that I wouldn't be out of ammo. But Klunk in Secret Agent Clank was also pretty tough.
years & years ago i would have said Dr. N! then DREK! then HOLY CRAP OTTO! Then recently… OMFG!!!!!!!!! KLUNK!!!!!!!!! U… EVIL LITTLE BUGGER!
but now… IDK they are soo easy… Guess Klunk? Nowdays i loose bout once or twice before killing him… WITHOUT the PDA! I hate the PDA! Never use it ever! And i have killed Drek with my Bomb Glaove (no PDA) Blaster (no PDA) and another challenge mode with the Pyricitor! (all gold) Beating him like 40 times makes you good at it! Same with Otto… But Klunk is a bit annoying… So to me (a guy with nothing better to do than set the goal of playing Ratchet & Clank longer than anyone else in the world) Klunk!
I HATED THE GIANT PROTOPET MONSTER!!!!!!!!!!!!!!I would be at the last bit of the the life of the protopet,AND I WOULD ALWAYS DIE!!! the enemies&tanks would shoot at you,and I would always die because of them.
I would always run out of ammo on most of my weapons.
I HATED THAT BOSS.
I HATE IT
I HATE IT
I HATE IT
From all my time playing Ratchet & Clank! (must be like 3 years of insane (almost) non stop playing i learnt a main BIG hint that can turn the tables pretty fast! I always thought The best way to avoid damage and kill big time! Is to jump! (with ze thumb) and shoot with your pointing finger bent down onto circle! (mainly when jumping) MAD! You say? Well you get use to it 
if you are already doing this!.. GREAT! You are top of the line! My two friends who thought they knew it all didnt know jumping could be as effective as it is refused to try it my way! Sadly one was far too stuburn & eventually got 'cool' but the other tried it… And once he learnt to change how he did things he became a Pro! Before then he always got stuck & got all moody (trying to break my PS2 ) but i step in and say… "must i do this? I could tell you some hints?" But he didnt care until after i killed Drek then got himthrough Magacorp HQ… Then he wanted to know
my point… Jump to dodge! (but in ACiT it doesent seem to go quite as smoothly… But i kept a x20 multiplyer through like four planets )
i found this helped my friend alot & i cant stand watching a person run into bullets because there were lines of fire comming in two directions that had him cornered.
I can't say about the PS3 games, but the PS2 ones.
Drek was okay, not hard. Thugs 4 Less boss in GC though, was pretty effin' annoying. Almost tough.
I hate the PDA! Never use it ever! And i have killed Drek with my Bomb Glaove (no PDA) Blaster (no PDA)
I don't like to use the PDA either. Too expensive! I usually only use it when fighting a hard boss and my weapons aren't leveled up all the way. 
I've been playing Ratchet & Clank for 11 years, but there are only a few games I haven't played yet. Since we're talking about bosses, I think that most of them are pretty easy if you have good weapons and move around a lot. So here is how I beat these bosses:
Drek: After I got to Veldin, before completing it I went back to the very first planet and went through all the planets again to get more bolts. I then went back to Blackwater City and bought the RYNO. It made Drek so easy to beat
Mutated Protopet: I did the same thing I did in the first game. Went back and bought the RYNO. The fight was over within minutes.
Dr. Nefarious from Ratchet & Clank 3: When I was younger, I found this boss extremely difficult. But now I just find it easy. He is super easy to beat if you have upgraded weapons
Vox: This boss wasn't too bad of a fight. I didn't have the Harbinger, so it made the fight a bit tough. I eventually got him though, using a fully upgraded Magma Cannon and Scorpion Flail.
Otto: Ok. I officially HATE this boss. It took me forever to beat him the first time, but I ended up doing it using a fully upgraded Shock Rocket, and Static Barrier. I still haven't beaten him in challenge mode though.
Klunk: I haven't played Secret Agent Clank.
Tachyon: I died a couple of times while beating this boss, and I had the RYNO and Alpha Disruptor. Those two weapons finished him off for me
Slag/Darkwater: Ha. I'm laughing at how easy this fight was. Alpha Disruptor quickly took him down.
Dr. Nefarious in A Crack in Time: This boss was pretty easy, but I kept falling off on the Hoverboot part. RYNO quickly finished him off.
Haven't finished All 4 One
Haven't finished QForce
Haven't played Nexus
Wow, quite the thread bump. Ok, I'll bite:
Drek: Just used the suck cannon. He kept spitting out mines so I didn't have to waste ammo. Plus, the blaster came in handy.
Thug-bot on Sneevilak: Forgot the turrets, just use your upgraded Heavy Bouncer and Meteor Gun and he'll be dead in no time!
Dr. Nefarious: Same thing: it's just a matter of having powerful weapons, which probably makes the boss level so fun and great.
No hard bosses in DL
SM: Luck.
SAC: Button mashin'
TOD: Tachyon is the 2nd hardest villain to beat for me, so I used the groovitron and Death springs in addition to the RYNO 4 and the Alpha Disruptor. Same with Slag and the Kerchu.
No hard bosses in QFB.
ACIT: When in doubt, spam buzz blades.
A4O: Without a RYNO 6 protosuit, defeating the final boss is hard, but possible.
FFA: Not even gonna…
ITN: Neftin was the only hard (and somewhat fun) boss to kill. A couple vortex grenades will kill him instantly.
Ps4: Snagglebeast: not very hard, just remember to strafe often, and shoot him while he's exposed on the ceiling. The blarg frogs won't attack, because they're slow.
These sound like some really good techniques. I'll try to remember these when playing the games I haven't completed:oui:
