I would recommend you:
Open site Explorer
Ahrefs
Backlinkwatch for checking the backlinks of your competitor's Website. They can give you full report of all the backlinks.

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I'd like to add majestic.com to the suggestions here since no one has mentioned it.

Ahrefs and Opensiteexplorer are all best

Another tool is: Backlink Checker

Have used SEO Power Suite for a long time now and it has multiple functionality that helps with all areas in regards to back links, rank tracking and competitor analysis.

Each of the components can be purchased on their own and the two I find most useful are their SEOSpyglass and Rank Tracker.

I've heard good things about Ahrefs but haven't really had to look elsewhere.

There are many tools for backlink analyzing of your compitators. Ahrefs.com is the best free tool for back link checking.

For quick checks and metrics, Majestic.com. For in depth backlink analysis, check all 3: OSE, Ahrefs, Majestic.

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Go for the semrush. It will help you to find all the keywords and backlinks of your competitor.

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I would recommended you only two online tools that you see in below :

1) Ahrefs.com
2) majestic.com

smallseotool is the best free online backlink checker.

I have subscriptions to all of the backlink checkers

The best one is Ahrefs, so go with that for now.

usually i used this.

majesticseo
open site explorer
ahrefs

they've limited analysis per ip. just reset ur modem or use vpn to get new ip

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More mass debation about a topic that has been beat to death.

Check the top of the forum. You see that button that says 'Search'?