Large Transport
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 3
Situational Awareness; Workload
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Human Factors; Procedure
During this session at R40 traffic volume and complexity were high. We were responsible for 15-20 aircraft. Aircraft X was in level flight at FL250 diverging North at ZZZ from Aircraft Y who checked in level at FL230 and was diverging east at ZZZ. I issued climb clearance to Aircraft Y on initial check in through Aircraft X.  When conflict alert activated I amended Aircraft Y's altitude to FL240 and the pilot said they were just passing through it. I was asked what I wanted them to do and I told them to descend back to FL240. I saw no reason to turn either aircraft as both were diverging would be separated within two updates.Standard separation was lost at 2.64 miles and 900ft. They were 4.14 miles and zero feet before achieving lateral divergence. I accept full responsibility for this error. Primary contributing factors were data block congestion and a close in scan failure. In total there were six aircraft within 12 miles of ZZZ. I just missed one.Conflict alert parameters could be increased to account for aircraft performance possibilities. These aircraft were two thousand feet apart and diverging in two minutes. Had conflict alert activated immediately after removing the temporary altitude this error could have been prevented. Two minutes and two thousand feet isn't outside the realm of possibility for most aircraft.
This loss of separation was directly a result of the reckless and unsafe methods of a ZZZ Center Controller. This sector was not busy; however he had put enough aircraft in conflict that he created the excess of complexity and these two were missed. There was no reason why this couldn't have been avoided! Controller prefers to put aircraft into conflict assuming he can control everything. This is not a rare occurrence but a constant practice! He put me in a position where I saw nothing safe happening. When I point out something unsafe I am told; 'That'll be fine'.Look back at this session and you will see that he is climbing aircraft though the same altitudes when there are overtakes and using no type of positive separation!Afterward when the situation is imminent he does something small that I feel only works because the pilots are getting TCAS advisories and adjusting their airspeed/rates of climb/decent on their own. I cannot keep up with working along someone with these practices. No one can; or should. In this case I wasn't able to keep up with this disregard for safety! I feel this is an intentional oversight by managers outside the control floor.  This person has had excessive loss of separation occurrences as well as excessive personnel conflicts since the beginning of his time at ZZZ Center. Nothing has been done. I am intensely frustrated that nothing is being done about this worker that will get people killed! Only action from outside this facility and outside the reach and shelter of this individuals local connections will result in change. This controller is proud of being difficult to work with and takes direct intentional action to ensure this. I hope someone outside ZZZ Center gets this and takes some kind of action. HELP! HELP!HELP! I couldn't be more serious! This is a desperate attempt for help.
Center Controller describes a loss of separation with two aircraft he was working. Numerous aircraft in the vicinity with data block congestion. Controller had separation; but elected to climb traffic through a diverging aircraft; having less than 5 miles. Another Controller reports that the working Controller is dangerous and puts aircraft in unsafe situations and watches.