T-62 - Thoroughly obsolete and all of the less than 30 in Ukrainian service are captured Russian vehicles uses a 115mm gun that no other tank does
T-64BV – Ukrainian designed and built [also saw limited service in the Soviet army] contemporary tank to the T-72 superior but more complicated and expensive to manufacture. Ukraine has a lot of them
T-72 - Ukraine had more than 1000 of various models of this tank, between their own, those donated from other countries and more than 300 captured from the Russians simple and robust its design like that of all later Soviet era tanks has a serious design flaw that cause it to explode violently killing the crew when taking a penetrating hit center mass
T-80UD - Ukrainian upgraded version of the Soviet T-80U has a much better engine, Ukraine produced about 500 of them
T-84M - Ukrainian upgrade of the T-80 only a handful in service
T-90 - Seriously flawed tank, all models in Ukrainian service are captured, this tank is probably inferior to Ukrainian T-64BVs, T-80UDs and T-84Ms in Ukrainian service
Polish PT-91 - a considerably enhanced T-72 with western electronics and optics
Slovenian M-55S - based on the 70 year old Soviet T-55 with bolt on armour, a 105mm gun and modern optics
Leopard 1A5 - Obsolete tank, decent gun and optics, very mobile, almost no armour close to 300 have been pledged, many require refurbishment
Leopard 2A4 - Original version of the Leopard 2 (turret cheeks and lower glacis are weak points)
Leopard 2A6 - Most advanced version of the Leopard made available to Ukraine
Strv 122 - Swedish improved Leopard 2A5 they only provided 10 of them
Challenger 2 - Probably the best tank in Ukraine at the moment, more than a match for anything the Russians have but they only have 14
M1A1 Abrams - First ones are supposed to be entering Ukrainian service right now Ukraine to receive 31