I have a set of Shimano M540 pedals on my bike which has Ultegra cranks on them. Shortly after installing these they started to creak when I put some decent pressure on them. I had to take them to a LBS because I could not remove them with a short 8mm wrench. The shop got them off cleaned the threads, re-greased them and put them back on using a torque wrench to get the proper tension/tightness. After this the bike was silent, all was great. Fast forward to me washing my bike and going out for a ride the creaking returned. I'm not sure what washing the bike did if anything it could have been a coincidence or not.

What I would like to ask the community here is what is the remedy for creaky pedals. I don't want to put lock-tite or teflon tape on them or something like that but this drives me crazy.

Maybe the problem isn't the interface between the pedal and the crank, but the interface between the pedal and the cleat/shoe

I agree with alcjphil that the shoes/cleats may be causing the noise, but what is wrong trying with PTFE tape on the threads? If you don't like it, it will peel right off. BTW, I use Tef-Gel and pedal washers on my pedals. No noises and easy to remove.

Buy yourself a proper pedal wrench, it's worth it.
Make sure everything is clean and regrease pedal threads.

But yes, it could very well be shoe cleats.
Process by elimination if possible, diff pedals etc

SPD creaking is the shoe- the cleat sets in a recess in the sole and when put into the pedals the outer edges of the pedals can rub against the rubber sole just out from the cleats. Trim a bit of rubber away or put a touch of grease on the soles just out from the cleats. I went through this and did the pedal tightening, cleat tightening, lube on the cleat all to no effect. Yep, drives you nuts it is the loudest noise from the bike by far, and irritating as heck.