unstoppable in English:

I was relentless in my pursuit

The situation will be particularly difficult because of the relentless population increase here.

a patient but relentless taskmaster

relentless efforts

a relentless fighter of evil

there is nothing we can do to stopthe relentless growth of social networking on the internet

relentless criticism/pressure

She told them he was relentless, the husband who always got his way.

"I have been relentless in trying to win the House back."

Her relentless determination to succeed surprised everyone.

relentless fight against crime

her relentless pursuit of perfection; a relentless enemy

after the massive and relentless housing construction...

To the public, this seemed like a relentless defense of order.

the relentless pursuit of wealth and power

the inexorable advance of time

Don't bother yourself with trying to convince him. He's inexorable.

And the argument here would be that the wheels of evolution grind slowly, but they are inexorable.