With investors waiting for the next catalyst to guide markets, the ASX chalked up a negative result for the week. Nonetheless, there were numerous companies that performed well, including new records from BHP and Afterpay, which led the way. At the close of trading this afternoon, the ASX 200 shed 0.6% for the week, settling on 6,715.40 points.

Which shares excelled?

Afterpay (ASX: APT) surged to a new all-time high this week, gaining 14.8% since last Friday. The move came as one of the company biggest international peers, Affirm (NASDAQ: AFRM), made its ipo debut on the US stock market, soaring more than 130% over the course of its first two days of trading.Also lifting sentiment across the sector was a strong trading update from Sezzle (ASX: SZL), which increased 19.8% this week. Momentum continued to build for the US-oriented BNPL player in the fourth quarter, with app downloads and merchant fee income soaring.Medical imaging technology company Pro Medicus (ASX: PME) had a bumper week thanks to a key contract award in the US. Shares in the company soared 17.1% after securing its largest contract thus far, a seven-year $40 million deal with Salt Lake City Intermountain Health.Coal stocks also had a positive week, with Whitehaven Coal (ASX: WHC) sounding the call for an optimistic outlook. As part of its December quarterly report the company took the opportunity to increase its sales forecast, with Asian coal demand expected to help sales return to pre-COVID levels.Thermal and metallurgical coal sale prices also improved during the quarter after August lows. New Hope Corporation (ASX: NHC) and Coronado Global Resources (ASX: CRN) were also buoyed by Whitehaven outlook, capping off a strong showing from the sector.Despite its share price gain being pared back significantly across the course of the week, Mesoblast (ASX: MSB) still ended up as one of the best-performers over recent days. The company started the week with positive news that its Rexlemestrocel-L treatment was seen to reduce the incidence of heart attacks, strokes, and cardiac death in patients with chronic heart failure.Elsewhere, Cimic Group (ASX: CIM) had a bright week after Moody Investors Service affirmed its rating, while Premier Investments (ASX: PMV) hit an all-time high in the wake of its soaring online sales showcased in its HY21 trading update. The retailer anticipates that EBIT for the half will come in at 75-85% higher than the prior corresponding half. Shares in PMV leapt 4.4% this week.Rounding things out, Pilbara Minerals (ASX: PLS) rally continued, Insurance Australia Group (ASX: IAG) rebounded firmly, Westpac (ASX: WBC) and Pointsbet Holdings (ASX: PBH) also had a standout week, while energy stocks Santos (ASX: STO) and Woodside Petroleum (ASX: WPL) gained ground on higher oil prices.

Which shares dragged on the market?

Tyro Payments (ASX: TYR) was subject to a wave of selling this week, diving 29.5% after the company outage issue extended further, and the stock was the subject of a short seller attack'. For over a week now a portion of the business' terminal fleet has been experiencing connectivity issues, with around 19% of its merchant customers impacted.The result of the outage is expected to drag on total transaction volumes (TTV). Adding to its woes, Tyro was also singled out by the same short seller that previously took aim at WiseTech Global (ASX: WTC), alleging that the terminal payments business was experiencing problems far greater than alluded to by management, however, Tyro has called a trading halt to respond to the accusations.Polynovo (ASX: PNV) trading update disappointed shareholders this week, with the stock dropping 28% in turn. Despite first-half sales rising by 31%, subdued sales growth in October and November meant that the second quarter of the half actually dragged on the overall result, with momentum seemingly slowing.Utilities businesses Meridian Energy (ASX: MEZ) and Contact Energy (ASX: CEN) were both lower this week amid contract news impacting New Zealand Aluminium Smelter (NZAS) at Tiwai Point.Gold stocks also had a dour week following the sharp drop in gold prices that took place last Friday after the ASX closed. When trading resumed on Monday morning, various gold miners and producers were hit particularly hard including Westgold Resources (ASX: WGX), Gold Road Resources (ASX: GOR), Perseus Mining (ASX: PRU), OceanaGold Corporation (ASX: OGC), Silver Lake Resources (ASX: SLR) and Evolution Mining (ASX: EVN).Some other high-profile names on the back foot this week were Costa Group (ASX: CGC), Adbri (ASX: ABC), Nanosonics (ASX: NAN), A2 Milk (ASX: A2M) and Altium (ASX: ALU), with the latter slammed by a first-half decline in revenue amid the impact of COVID in Europe and the US, plus compliance licencing issues in China.

We'll be back next week with another Weekly ASX Trading Wrap Up - until then, have a great week!