What do u have to unclog toilet? Need strongest have tried everything else.

I agree with Quentin. If plunger and other things aren't working, try a toilet snake to physically clear the blockage. As a last resort, the blockage may be near the O ring, just under the base of the toilet. If the snake doesn't work, the blockage may be stuck in this area, especially if it's not toilet paper or other compostable material. Accidentally flushing solid material, hair brush, toys, plastic, tampons, pads, etc. could cause a blockage and allow T.P. and other things to build upYou can turn off the water to the toilet, flush it to clear the water and get it out of the bowl, then remove the 2 bolts at the base and pull the toilet away from pipe in the floor. If the block is in this area, you'll see it in the pipe, and be able to clean it out. You'll need to buy a new O ring and put it on before you put the toilet back and bolt it to the floor. As Quentin said, it could be further down the line in the pipe, maybe at an elbow or turn in the pipes. May need a plumber for that.

They sell a 'toilet snake', if that doesn't work, it may be clogged further down the sewer line. Good luck.