A young guy starts an small scale enterprise instead of going with the regular job after his graduation, but as his enterprise starts making profits he realizes the large scale enterprise wants to crush his firm.

A key to helping the reader visualize a logline is specifics

A young guy vs A shy veterinarian student — If you say, a young guy it doesn’t tell us much but if you give us a bit of personality or a job description we can visualize the character better

Small scale enterprise vs opens dog psychologist business — A small scale enterprise is too vague, is he selling hats, is he creating websites? What business?

Instead of going with a regular job — Don’t need it in the logline

After graduation — Again this does not seem to have any bearing on the plot. Don’t need it.

but as his enterprise (again vague, give us a specific enterprise)

starts ?making profits — I think this can just be implied a little later in the logline, a large scale enterprise wouldn’t want to crush him if he was a failure.

The large scale enterprise– vague, name the corporation, is it Purina? is it McDonald’s? Or at least give us a specific description.

wants to crush his firm– I would also put a face on the corporation, give us ?a specific person that wants to crush him… Is it his jealous more successful brother, is it a former best friend… is it Bill Gates?

Adding a few specifics will give the reader a more clear picture of your logline and make the logline far more enticing.

Hope that helped

btw, your idea may be great, just saying the logline needs more specifics to reflect and sell your story to the reader.