Well, his announcement that Hillary was clear, his bending over for Lynch, his re-announcement of the Hillary "matter", his weakness around everything Trump, his apparent shock at Trumps "suggestion" even thou he'd obviously faced this before - see Lynch, his allowing himself to discuss cases in private with Trump, his refusal to clear Trump, his refusal to call out the "fake media", starting a personal file against the president, leaking to the press, used his memos to manipulate the government, dragging his friend into a scandal, lying to the president.
These things (and i'm probably forgetting a lot) all came to light yesterday - I wonder just how much we don't know. Now, you'll likely defend some of these questionable decisions as defense or done out of necessity, but everything he has done, he could've done something else - something better or more honest. He chose the worst path nearly every time he had a decision to make.
He was also stringing the president along and giving him the obviously empty "we'll see" routine - a routine we use for our kids when we actually have no intention to do anything. This alone should've had him fired and really the last time they talked, this was the conversation and the lie Comey gave to the president. Is it possible that Trump saw through this thinly veiled lie and decided that that was enough - I think so!