This is as complete a list as you will find for flights going to Agadir. To make things easier, I personally recommend Skyscanner, but if you want to search things out for yourself, be my guest!

They are organized by country of origin:

Belgium
Brussels- Ryanair
Brussels Intl- Atlas Blue, Jetairfly
France
Marseilles- ryanair
paris cdg- easyjet, atlas blue
paris ory- atlas blue
Germany
cologne- tuifly
munich- condor
Italy
Milan Orio al Serio- ryanair

Morocco
Casablanca- air arabia

Netherlands
Amsterdam- atlas blue

Spain-Barcelona- jet4you, atlasblue
madrid barajas- easyjet, atlas blue
Switzerland
Geneva- baboo
UK- London Heathrow- Atlas blue