When you get to the top of Porky's building, Porky will trick you and get 10 of his robots to attack you. They have PSI shields that give you back the damage that you gave to them. PK Love (or whatever you called it) or PK Starstorm will make you faint unless you can quickly heal yourself. Each of them have about 900hp (865 to be exact). Kumatora's PK Thunder will do damage that won't get reflected, but it takes a while to do kill them one at a time. PK Ground doesn't do much either.
But, like the title says, there is an easier way.
Fire doesn't work good against them. Their PSI shields only last for three hits. What does that tell you
Use Kumatora's weakest PK Fire three times, and the shields are gone. :D
Her PK Fire only does around 10 damage, so you won't get much damage reflected back at you.
While you're destroying their shields, you can either normally attack them, up your offense or defense, or lower their offense or defense. After their shields are destroyed, it's easy to kill them with PK Love or PK Starstorm.
After they're all gone, go and get Lucas to pull the final needle. :D