The best enginerring college in tamil nadu is 

IIT MADRAS- chennai. To get admission there you need to crack jee advanced with high score. It is one of the premier institute in India. And also its placement is very good. It is the best college in TN.

NIT trichy - It is the second best engineering college in India. To get admission in this college you have to crack jee main with very good marks. Placement scenario is good here.

MIT chennai- it accepts jee main score for admission. 

Other good colleges are- vit,srm etc

And there are lots of more college ,you can find it in the link

Https://engineering.careers360.com/colleges/list-of-engineering-colleges-in-tamil-nadu

Hope it helps!