Looking on the internet deeply has found these results:

Serious is the most popular phrase on the web.

Intense 1508,000,000 results on the web	Serious 1876,000,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
Top: Intense freshness with peppermint and lavender. Class III V sections. Intense rapids within the tropical rainforest. Intense reaction continues following Dr. Reed's shocking announcement. Heart: Intense and pungent saffron. So Intense is a volumizing and fortifying mascara. She also has these... Intense mood swings. Intense deep greenblue, mat eyeshadow.	Serious misconduct includes the following situations: marketing experience for bivalirudin. Serious antiepileptic drug hypersensitivity syndrome has occurred in association with rufinamide therapy. There Was A Time When Christian Was A Serious Academic. Serious bleeding, including bleeding with a fatal outcome has been reported in post Serious and persistent violation of religious freedom by the Russian authorities Serious enough for Dunne to make me Acting Lieutenant. Serious as a hangnail, honey.

Intense

1508,000,000 results on the web

Serious

1876,000,000 results on the web

More popular!

Serious misconduct includes the following situations:
marketing experience for bivalirudin.
Serious antiepileptic drug hypersensitivity syndrome has occurred in association with rufinamide therapy.
There Was A Time When Christian Was A Serious Academic.
Serious bleeding, including bleeding with a fatal outcome has been reported in post
Serious and persistent violation of religious freedom by the Russian authorities
Serious enough for Dunne to make me Acting Lieutenant.
Serious as a hangnail, honey.