I only hate having to use certain Mechs, I generally don't hate facing a specific 'Mech.
HOWEVER...
In our Narrative Campaign Commandos, Urbanmechs, and Javelins seem to get the short end of the stick from us.
For Commandos, I think it is just they tend to be the easiest to kill when they are on the board, but it could also be that our (as well as my) first 'Mech loss was when a Commando managed to get behind my Thunderbolt and TAC it's lower LRM Ammo Bay from the Rear (or was it a TAC?).
Urbanmechs just happen to be in a luckless state when we usually bring a lot of Jumpers in to where we face them, so can be outmaneuvered by anything. We've managed to secure one ourselves, but the funniest thing is that for most of them, we always Crit the AC/10 before it can really do much. The last one got hit by a Long Tom's scatter shot, lost its AC/10, and then tried to retreat. Then when we tried to hit its bigger brother the Centurion, it scattered back to slap the Urbanmech even more!
The Javelin, though, has reached a place of immediate loathing in our hearts thanks to 2 specific missions. Our GM has us face off against Black Inferno every now and then due to finding some funny Mechs in a Leopard out in the Periphery one time (come to think of it the Widows were interested in it, too). They also tend to hit us with some fancy advanced (and sometimes custom Mechs).
In our previous series, we see a Javelin. We expect it to be the Fire Javelin, because it's naturally more Scary, right? Nope. Well, then it has some advanced tech and customization, right? Nope. Just the standard JVN-10N with 2 SRM-6s. Then it fired. Infernos. We were busy pulling out, and he had some heavier stuff backing it up, too, so we didn't deal with it then.
After a couple more missions, we get ambushed by Black Inferno again, and there's that same Javelin. It rushes up and puts both racks in to one of our Awesomes and it starts baking. We focus fire on it, and it goes down so fast we basically say it became a puddle. We later learned that the pilot had the Sandblaster Special Pilot Ability, too, which means the closer it got, the more missiles would likely hit.
We're now in the Ronin Wars, helping out the local Rasalhague transition government survive the Lyran Duke's attentions. We saw a Javelin came in, and we're all, "F*** THAT GUY!", not even trusting it to NOT have Infernos.