Viserys

When I first crossed over, I thought the most insidious enemy was Varys.

I killed Varys.

After getting rid of Varys, I thought the most insidious enemy was Illyrio.

I killed Illyrio.

I killed Illyrio and I slew the centaurs.

The destruction of the Centaur Free Cities has become my biggest worry again!

ah,

I understand more and more now.

My greatest and most sinister enemy is not Robert, not the White Walkers,

He's right above my head!

He is the high and mighty god worshipped by everyone!