How does one check for competition?

What tools do you use to determine whether a certain niche/keyword is worth fighting for or not?

ahrefs is one of the best and easiest to use. Add in a bit of common sense and SEO experience into the analysis and you'll find a lot of good keywords worth fighting for.

As for long tails, KeywordSnatcher and KeywordsEverywhere are good tools, as well. They can find you 1000s of great long tails in any niche.

Regarding niches "worth fighting for", every niche that meets these criteria is worth fighting for....

- is profitable (people spend money on it, day and night);
- is popular (has millions / billions of monthly searches for all of their keywords combined);
- is part of the 4-5 ultra big niches that have both high spending numbers and high monthly searches: health / medical, technology, relationships, finances. These 4-5 niches are ultra popular (and also ultra competitive, too, as a result of their popularity) and if you go into either of them (but doing your keyword research properly, obviously to avoid high competition) you will make a killing with them

There are other niches out there that could be profitable (therefore, worth fighting for), like self improvement, crafts & hobbies, web services (logo design, web hosting, etc), or seasonal niches like swimming pool cleaning, or christmas / easter / whatever related services, but these are usually harder to get into for newbies because the competition is high because the spending is also high on these niches. But they are worth fighting for, as well, which is why I mentioned them

I had used long tail pro.

I usually trust Ahrefs data for backlinks and Semrush data for keywords. There are plenty of other tools and you should test multiple tools to see which one suits your needs better.

Ahrefs is number one tool.

You should make a good list of the keywords you'd be targeting for such a niche,
To decide what makes it worth it or not, you should ask yourself these questions

• are you able to rank for any of these keywords?
• is there plenty of keywords? is it scalable?
• how much you'll be spending in terms of efforts, time & money?
• how much you'll earn from this?
• is it a long-term investment?

Typically, any niche with a good ROI which you can invest in is simply worth it,
you're doing it for profiting after all