Basset hound being aggressive?

I have a 7 year old basset hound, but between 3-7 years old he became aggressive, he would not let us put the collar or the harness on him, he would bite whoever, even my dad who he "respected" the most, we did not even try to bathe him because we knew he would bite us (and hard, it was not even a "warning" bite). Now that he is 7 years old and I am back to my parents home, I have taken the time to give him all the attention possible, pet him, brush him, I was able to put the harness on him and we went for a walk, then I was able to bathe him, yesterday I was able to give him dewormer tablets where I had to grab his muzzle several times and no problem. So I was wondering if anyone else had an experience like this as well where their basset became more aggressive? And what’s your theory about it?

I have a 7 year old basset hound, but between 3-7 years old he became aggressive, he would not let us put the collar or the harness on him, he would bite whoever, even my dad who he "respected" the most, we did not even try to bathe him because we knew he would bite us (and hard, it was not even a "warning" bite). Now that he is 7 years old and I am back to my parents home, I have taken the time to give him all the attention possible, pet him, brush him, I was able to put the harness on him and we went for a walk, then I was able to bathe him, yesterday I was able to give him dewormer tablets where I had to grab his muzzle several times and no problem. So I was wondering if anyone else had an experience like this as well where their basset became more aggressive? And what’s your theory about it?