I meant that electromagnetism is ubiquitous in its role in the nature of ordinary matter itself.

Are magnet’s the most dangerous thing in the universe?

No, not even remotely. That's not to say that the extreme magnetic fields of magnetars wouldn't be awesomely dangerous, but "most dangerous thing in the universe" is an absurdly high bar to meet.

After all Blackholes are powerful magnets

The accretion disk consisting of material surrounding a black hole is capable of generating strong magnetic fields, rather than the black hole itself.