Wladimir Klitschko retained his WBA, IBF and WBO heavyweight titles, unanimously outpointing Poland's Mariusz Wach on Saturday night.
The 6-foot-7 1/2 Wach was the tallest opponent Klitschko has faced in his 16-year professional career, but offered little threat against the faster Ukrainian.
The judges scored it 120-107, 120-107 and 119-109 for Klitschko, who was troubled only at the end of the fifth round, when Wach surprised him with a right hook before a flurry of punches.
'I want to remember one man, who can't be here today unfortunately. Emanuel Steward, we miss you, we're thinking of you.' —Winner Wladimir Klitschko, addressing the Hamburg crowd after the bout
"He caught me in the fifth, but then I slipped," said Klitschko, who was left with a small cut under his left eye.
Klitschko left the 32-year-old Wach wobbling in the seventh with a devastating right followed by a series of combinations. Wach displayed incredible stamina to continue.
"That was the hardest fight of my career," Wach said after his first loss. "I want to apologize to everyone for not living up to expectations. I really wanted to win. Thank you so much to my family."
The 36-year-old Klitschko improved to 59-3 (51 KOs), and Wach dropped to 27-1 (15 KOs).
Klitschko said Wach "boxed brilliantly."
Klitschko was fighting for the first time since the death of his longtime trainer and friend Emanuel Steward.
"I want to remember one man, who can't be here today unfortunately. Emanuel Steward, we miss you, we're thinking of you," Klitschko said.
Fans also paid tribute to the late American before the bout when the bell was rung 10 times in his memory. Steward, who was in Klitschko's corner for nine years, died at the age of 68 on Oct. 25.
"It was hard for [Wladimir], very hard," said Vitali Klitschko, referring to his younger brother's preparations following Steward's death.
The older Klitschko, who holds the WBC belt, said the fight "was unbelievably brutal. [Wach] just didn't want to fall. He somehow kept standing."
Sylvester Stallone greeted fans beforehand as part of the promotional campaign for the Rocky musical which opens in Hamburg on Nov. 18.
Mares wins in L.A.
Abner Mares attacked relentlessly on the way to a unanimous decision over Anselmo Moreno on Saturday night in Los Angeles, defending his WBC 122-pound title and handing Moreno his first defeat in a decade.
Mares (25-0-1) rarely stopped moving forward in a brawl with Moreno (33-2-1), the elusive Panamanian star. In the fifth round, Mares scored the first career knockdown of Moreno, who had won 27 straight fights since October 2002.
Leo Santa Cruz also defended his IBF bantamweight title, stopping Victor Zaleta in the ninth round of a brutal fight on a thoroughly entertaining card at Staples Center.
Alfredo Angulo stopped Raul Casarez with a single left hook 56 seconds into the first round, making a dramatic return to the ring after a year away.
Earlier, Welsh light heavyweight Nathan Cleverly defended his WBO title with an eighth-round stoppage of Shawn Hawk.