When I say the last boss, I meant Trypticon. At least for Omega Supreme, you can drive around to avoid his attacks, but that was not the case for Trypticon. It's hard to dodge his attacks because the space is so small, and there is practically no place to take cover. 

While driving to get to Trypticon there is an Autobot medical camp to the right close to starting location.
Wait a few seconds there an one of them will unlock some door for you where there will be armor.
 
1st phase:
Race to the top level while he talks. 
Activate switch.
Drive/jump to the right ledge.
Stand behind the metal barrier/outcropping moving a bit from time to time.
(you will still get hit but some shots will hit the wall and the rest your armor can take for a while)
Shoot barrels.
Repeat for second set of barrels.
 
2nd phase:
Use Bumblebee and keep using dash while strafing.
Don't take cover, just keep moving side to side.
Take shots at the exposed heat sinks when you get time.

There is a pillar/overhang along the left side (if you are facing him) that will protect you from a lot of his attacks. Especially in the last phase w/ the missiles. You'll really only have to look out for the tail attack, and the spiders.

Hammerjelly pretty much nailed it.  Trypticon is a pain, but he isn't impossible.  The only thing is that you have to peek out of cover from time to time, and Optimus is too huge for any of the cover in that area, so yeah, stick to Bee.

I always get hit w/ the tail though, if anyone knows a good way to avoid it I think it would be helpful when I play this game on Hard.

I just beat him using optimus. 

Took me a while to beat him solo on Hard using Optimus. Until I got the routine down perfectly, I would die. You can't afford to get hit by anything that guy throws at you on hard. Heh.

Once you figure it out, it's pretty easy. The first and second attacks (Missiles, energy missiles) can be outrun by driving or using dash. The tail telegraphs which side of the screen it's going to attack, so just stick to the middle and then move to the opposite side once the tail lights up. Then just keep shooting the cores until the spiders burst out. Sometimes you can let them come and get a couple extra shots in.